OK. Here's something to consider. If you make these changes to the patches, they'll need to be saved in user locations, or you'll need to do it every single time you need that patch. I haven't noticed the problem that much with my xp80. You might consider buying a stereo compressor/limiter to run your synthe through. That might help equalize the volume fluctuations you're experiencing.
As far as the 60s 70s board, while some of the organ sounds are similar to stock sounds, most imo are much better. Plus there are many organ samples with real leslie applied, so you don't need to use the soso simulation in the XP FX. Rhodes sounds are a bit noisy sometimes, and they don't really hammer. They're more ballad or jazz oriented. Wurlis are pretty good. I've tweaked a couple rhodes and wurli sounds to get them more authentic, at least to me they sound more authentic. I like the board a lot, because the XP stock sounds rhodes don't sound anything like the real thing, and it doesn't even have wurlis. This board has helped a lot. i just wish the organs and rhodes could be made a bit more gritty. I'm looking to buy a preamp for that purpose. I'd really miss the expansion board if it went wrecked somehow, which I doubt.