I have a couple core 904's, really should play around like you're doing in case I have something there I can build up. Will admit don't know crap about them, bought them cheap and quite awhile ago.
Yeah.. most things that are not high performance for these cars is really not that expensive. I had a stock, non-Sure Grip 7ΒΌ rear that I monkeyed around with before I did work on the rear brakes.