Thanks. I also found and read that thread.
I am indeed trying to deploy a stack. Perhaps it’s possible to deploy a container on a node with a static IP but not a stack with replication set. Unfortunately that’s the entire reason I built the swarm 
For the time being I have deployed pihole the old fashioned way by exposing ports on the host. All DNS traffic appears to come from the host, but I can live with that for the time being. The frustrating thing is; when ever the cloudflared VM is deployed it gets a new IP and I have to update pihole to restore DNS in my environment.
I tried using smaller subnets, such as a /30 so that there were only 2 IPs available, however it appears that docker won’t deploy the containers to anything smaller than a /29.
Every time I think I’ve found a suitable workaround, there’s something else.