I know it's probably not something you want to hear after having spent money on the silicone neck seal....but if you can't find some way to mitigate these issues, I think your best bet is going with a neoprene neck seal. Some buddies of mine used to get the "hangman's neck" really badly, but as soon as they switched to neoprene, no more issues. I really like the neoprene -- feels much less constricting, warmer, won't fail catastrophically (they age gracefully....and when you start noticing a bit of leakage, it's very easy to cut a wedge out of the seal and glue it back together, making for a good seal for another couple hundred dives).
I assume the bioseal will not have any negative effects on the silicone (??) but it will kill latex seals quickly....maybe after ten or so dives [just a tidbit for anyone reading who might consider using it with their latex seals].