I have been running distributed flip sims on our farm and it has been working very well. We can can get a traditional 14hr sim back in 2-3 hours distributing it into 5 clusters. The tank in this case needs to be fairly deep so I tried optimizing further by making it a narrow band sim, however as soon as it is setup for narrow band the distributed sims seem to splash up and down at the interface between clusters whereas the interface was imperceptible before using narrow band.. Distributed Pressure Solve is being used in both cases.. There is a section in the docs called “Set up a distributed narrow band FLIP tank” so I assume it's supported (I am in H17.5)? Is there anything special I need to consider when distributing a narrow band flip sim?

And for the record- A 5 cluster distributed sim finishes in 2-3 hours, and a non-distributed narrow band sim also finishes in about 3 hours and does not look qualitatively different.

AFAIK SideFX added the option of distributed narrowband sims in H18. Might have also been backported to a late 17.5 version.
Try searching for it in the changelog.

Apparently distributed narrow band simulation support was a feature release in 17.5:
https://www.sidefx.com/docs/houdini/news/17_5/index.html#fluids [www.sidefx.com]

My bad, but that's a weird one then.

Maybe check the setup again and if that fails contact support@sidefx.com. Not a lot of users run distributed narrow band sims I'm guessing.