Can a multi-node Cassandra cluster be secured in the DO cloud?

I’m configuring the internode connection for Cassandra 3.5, though the same question applies to older versions, also.

In cassandra.yaml, there’s this:

# SSL port, for encrypted communication.  Unused unless enabled in
# encryption_options
# For security reasons, you should not expose this port to the internet.  Firewall it if needed.
ssl_storage_port: 7001

...

server_encryption_options:
    internode_encryption: all

Now, binding to a non-routable NIC will ensure that it’s not exposed outside DO, but it will be exposed to other DO VMs. Is there a way within DO to make this more secure? I don’t see anything about private networking support from DO.

I’ve read Introducing Private Networking, but that doesn’t block others’ droplets from seeing my traffic, so it’s not what I would consider private networking.