It was in vanilla power armor Mk II, but I think rampant arsenal was messing it up. I disabled rampant arsenal's equipment additions/modifications, which appeared to fix it. As for other compatibility, I'm not sure if it's currently compatible with power armor MK IV - but that would be a lovely addition, for sure! One other minor thing is that the guns don't recognize extended/compressed ammo from the more ammo mod, but I think that could end up being a bit of a pain to change given their implementation of how those magazines actually work. Figured I should mention just to be safe, though.
Thank you!