what exactly is incompatible? OP+4.0 is just a shiplist and models, and the enhancement pack has two model test missions so I would think Firesoul's mod would work great in the pack.
*sigh* that's the thing, I don't remember what the exact nature of the the problem was.
The Enhancement pack does actually have a bunch of stuff with it other than OP+4.0 and some models, tho...
Only that Bonk had strongly recommended not to use the pack, but to use his thread and links instead.
And, I have discovered that Bonk really knows his s*** when it come to this sort of stuff and trust his recommendations.
I did actually try a couple searches for this info, but, after 45 min of quick-reading dozens of threads, I was unable to find the thread he posted about it.
I was hoping someone with a better memory than me would post with the more technical aspects of the issue with Pesty's Enhancement pack actually.
And, with my basically trial and error knowledge, I'm not even sure if it's the source of your problem.
I'm rapidly running out of ideas to help ya...