diff --git a/beacon_node/Cargo.toml b/beacon_node/Cargo.toml
index 3107068d9..47abb6c6d 100644
--- a/beacon_node/Cargo.toml
+++ b/beacon_node/Cargo.toml
@@ -10,7 +10,6 @@ types = { path = "../eth2/types" }
 toml = "^0.5"
 store = { path = "./store" }
 client = { path = "client" }
-fork_choice = { path = "../eth2/fork_choice" }
 version = { path = "version" }
 clap = "2.32.0"
 slog = { version = "^2.2.3" , features = ["max_level_trace", "release_max_level_debug"] }
diff --git a/beacon_node/client/src/beacon_chain_types.rs b/beacon_node/client/src/beacon_chain_types.rs
index 133ebcc94..c55c04b44 100644
--- a/beacon_node/client/src/beacon_chain_types.rs
+++ b/beacon_node/client/src/beacon_chain_types.rs
@@ -1,18 +1,14 @@
 use beacon_chain::{
-    fork_choice::OptimizedLMDGhost,
-    slot_clock::SystemTimeSlotClock,
-    store::{DiskStore, MemoryStore, Store},
-    BeaconChain, BeaconChainTypes,
+    fork_choice::OptimizedLMDGhost, slot_clock::SystemTimeSlotClock, store::Store, BeaconChain,
+    BeaconChainTypes,
 };
 use fork_choice::ForkChoice;
 use slog::{info, Logger};
 use slot_clock::SlotClock;
+use std::marker::PhantomData;
 use std::sync::Arc;
 use tree_hash::TreeHash;
-use types::{
-    test_utils::TestingBeaconStateBuilder, BeaconBlock, ChainSpec, EthSpec, Hash256,
-    MinimalEthSpec,
-};
+use types::{test_utils::TestingBeaconStateBuilder, BeaconBlock, ChainSpec, EthSpec, Hash256};
 
 /// The number initial validators when starting the `Minimal`.
 const TESTNET_VALIDATOR_COUNT: usize = 16;
@@ -28,27 +24,19 @@ pub trait InitialiseBeaconChain<T: BeaconChainTypes> {
     }
 }
 
-/// A testnet-suitable BeaconChainType, using `MemoryStore`.
 #[derive(Clone)]
-pub struct TestnetMemoryBeaconChainTypes;
-impl BeaconChainTypes for TestnetMemoryBeaconChainTypes {
-    type Store = MemoryStore;
-    type SlotClock = SystemTimeSlotClock;
-    type ForkChoice = OptimizedLMDGhost<Self::Store, Self::EthSpec>;
-    type EthSpec = MinimalEthSpec;
+pub struct ClientType<S: Store, E: EthSpec> {
+    _phantom_t: PhantomData<S>,
+    _phantom_u: PhantomData<E>,
 }
-impl<T: BeaconChainTypes> InitialiseBeaconChain<T> for TestnetMemoryBeaconChainTypes {}
 
-/// A testnet-suitable BeaconChainType, using `DiskStore`.
-#[derive(Clone)]
-pub struct TestnetDiskBeaconChainTypes;
-impl BeaconChainTypes for TestnetDiskBeaconChainTypes {
-    type Store = DiskStore;
+impl<S: Store, E: EthSpec + Clone> BeaconChainTypes for ClientType<S, E> {
+    type Store = S;
     type SlotClock = SystemTimeSlotClock;
-    type ForkChoice = OptimizedLMDGhost<Self::Store, Self::EthSpec>;
-    type EthSpec = MinimalEthSpec;
+    type ForkChoice = OptimizedLMDGhost<S, E>;
+    type EthSpec = E;
 }
-impl<T: BeaconChainTypes> InitialiseBeaconChain<T> for TestnetDiskBeaconChainTypes {}
+impl<T: Store, E: EthSpec, X: BeaconChainTypes> InitialiseBeaconChain<X> for ClientType<T, E> {}
 
 /// Loads a `BeaconChain` from `store`, if it exists. Otherwise, create a new chain from genesis.
 fn maybe_load_from_store_for_testnet<T, U: Store, V: EthSpec>(
diff --git a/beacon_node/client/src/lib.rs b/beacon_node/client/src/lib.rs
index ae28858c5..c4e1c2558 100644
--- a/beacon_node/client/src/lib.rs
+++ b/beacon_node/client/src/lib.rs
@@ -19,8 +19,8 @@ use tokio::runtime::TaskExecutor;
 use tokio::timer::Interval;
 
 pub use beacon_chain::BeaconChainTypes;
+pub use beacon_chain_types::ClientType;
 pub use beacon_chain_types::InitialiseBeaconChain;
-pub use beacon_chain_types::{TestnetDiskBeaconChainTypes, TestnetMemoryBeaconChainTypes};
 pub use client_config::ClientConfig;
 
 /// Main beacon node client service. This provides the connection and initialisation of the clients
diff --git a/beacon_node/rpc/src/lib.rs b/beacon_node/rpc/src/lib.rs
index f2f1b2abf..11de6eb6a 100644
--- a/beacon_node/rpc/src/lib.rs
+++ b/beacon_node/rpc/src/lib.rs
@@ -27,7 +27,8 @@ pub fn start_server<T: BeaconChainTypes + Clone + 'static>(
     network_chan: crossbeam_channel::Sender<NetworkMessage>,
     beacon_chain: Arc<BeaconChain<T>>,
     log: &slog::Logger,
-) -> exit_future::Signal {
+) -> exit_future::Signal
+{
     let log = log.new(o!("Service"=>"RPC"));
     let env = Arc::new(Environment::new(1));
 
diff --git a/beacon_node/src/run.rs b/beacon_node/src/run.rs
index 0638e9ec9..4e2ea0876 100644
--- a/beacon_node/src/run.rs
+++ b/beacon_node/src/run.rs
@@ -1,10 +1,9 @@
 use client::{
-    error, notifier, BeaconChainTypes, Client, ClientConfig, InitialiseBeaconChain,
-    TestnetDiskBeaconChainTypes, TestnetMemoryBeaconChainTypes,
+    error, notifier, BeaconChainTypes, Client, ClientConfig, ClientType, InitialiseBeaconChain,
 };
 use futures::sync::oneshot;
 use futures::Future;
-use slog::{error, info};
+use slog::{warn, error, info};
 use std::cell::RefCell;
 use std::path::Path;
 use std::path::PathBuf;
@@ -13,6 +12,7 @@ use tokio::runtime::Builder;
 use tokio::runtime::Runtime;
 use tokio::runtime::TaskExecutor;
 use tokio_timer::clock::Clock;
+use types::{MainnetEthSpec, MinimalEthSpec};
 
 pub fn run_beacon_node(config: ClientConfig, log: &slog::Logger) -> error::Result<()> {
     let runtime = Builder::new()
@@ -27,16 +27,22 @@ pub fn run_beacon_node(config: ClientConfig, log: &slog::Logger) -> error::Resul
         .db_path()
         .ok_or_else::<error::Error, _>(|| "Unable to access database path".into())?;
     let db_type = &config.db_type;
-    let spec_constants = &config.spec_constants;
+    let spec_constants = config.spec_constants.clone();
 
     let other_config = config.clone();
 
     let result = match (db_type.as_str(), spec_constants.as_str()) {
-        ("disk", "testnet") => {
-            run::<TestnetDiskBeaconChainTypes>(&db_path, config, executor, runtime, log)
+        ("disk", "minimal") => {
+            run::<ClientType<DiskStore, MinimalEthSpec>>(&db_path, config, executor, runtime, log)
         }
-        ("memory", "testnet") => {
-            run::<TestnetMemoryBeaconChainTypes>(&db_path, config, executor, runtime, log)
+        ("memory", "minimal") => {
+            run::<ClientType<MemoryStore, MinimalEthSpec>>(&db_path, config, executor, runtime, log)
+        }
+        ("disk", "mainnet") => {
+            run::<ClientType<DiskStore, MainnetEthSpec>>(&db_path, config, executor, runtime, log)
+        }
+        ("memory", "mainnet") => {
+            run::<ClientType<MemoryStore, MainnetEthSpec>>(&db_path, config, executor, runtime, log)
         }
         (db_type, spec) => {
             error!(log, "Unknown runtime configuration"; "spec" => spec, "db_type" => db_type);
@@ -53,6 +59,23 @@ pub fn run_beacon_node(config: ClientConfig, log: &slog::Logger) -> error::Resul
             "spec_constants" => &other_config.spec_constants,
             "db_type" => &other_config.db_type,
         );
+
+        // `SHUFFLE_ROUND_COUNT == 10` in minimal, this is not considered safe.
+        if spec_constants.as_str() == "minimal" {
+            warn!(
+                log,
+                "The minimal specification does not use cryptographically secure committee selection."
+            )
+        }
+
+        // Mainnet is not really complete, it still generates determinitic, unsafe initial
+        // validators.
+        if spec_constants.as_str() == "mainnet" {
+            warn!(
+                log,
+                "The mainnet specification uses unsafe validator keypairs."
+            )
+        }
     }
 
     result
@@ -66,7 +89,7 @@ pub fn run<T>(
     log: &slog::Logger,
 ) -> error::Result<()>
 where
-    T: BeaconChainTypes + InitialiseBeaconChain<T> + Send + Sync + 'static + Clone,
+    T: BeaconChainTypes + InitialiseBeaconChain<T> + Clone + Send + Sync + 'static,
     T::Store: OpenDatabase,
 {
     let store = T::Store::open_database(&db_path)?;
diff --git a/beacon_node/store/src/leveldb_store.rs b/beacon_node/store/src/leveldb_store.rs
index 09aec46fa..699861e3a 100644
--- a/beacon_node/store/src/leveldb_store.rs
+++ b/beacon_node/store/src/leveldb_store.rs
@@ -5,10 +5,14 @@ use leveldb::database::Database;
 use leveldb::error::Error as LevelDBError;
 use leveldb::options::{Options, ReadOptions, WriteOptions};
 use std::path::Path;
+use std::sync::Arc;
 
 /// A wrapped leveldb database.
+#[derive(Clone)]
 pub struct LevelDB {
-    db: Database<BytesKey>,
+    // Note: this `Arc` is only included because of an artificial constraint by gRPC. Hopefully we
+    // can remove this one day.
+    db: Arc<Database<BytesKey>>,
 }
 
 impl LevelDB {
@@ -18,7 +22,7 @@ impl LevelDB {
 
         options.create_if_missing = true;
 
-        let db = Database::open(path, options)?;
+        let db = Arc::new(Database::open(path, options)?);
 
         Ok(Self { db })
     }
diff --git a/beacon_node/store/src/memory_store.rs b/beacon_node/store/src/memory_store.rs
index 086a16c26..048c054f5 100644
--- a/beacon_node/store/src/memory_store.rs
+++ b/beacon_node/store/src/memory_store.rs
@@ -1,19 +1,23 @@
 use super::{Error, Store};
 use parking_lot::RwLock;
 use std::collections::HashMap;
+use std::sync::Arc;
 
 type DBHashMap = HashMap<Vec<u8>, Vec<u8>>;
 
 /// A thread-safe `HashMap` wrapper.
+#[derive(Clone)]
 pub struct MemoryStore {
-    db: RwLock<DBHashMap>,
+    // Note: this `Arc` is only included because of an artificial constraint by gRPC. Hopefully we
+    // can remove this one day.
+    db: Arc<RwLock<DBHashMap>>,
 }
 
 impl MemoryStore {
     /// Create a new, empty database.
     pub fn open() -> Self {
         Self {
-            db: RwLock::new(HashMap::new()),
+            db: Arc::new(RwLock::new(HashMap::new())),
         }
     }