Ron,
I would start with test days, just for that; to test changes. And treat a few race weekends as test days. And make one small change per track session. This is one of the things that makes this sport expensive. I think you are right about the springs, you might want to go softer but I don't know how much, it would be more forgiving at first. If I had the money I'd hook up with a shop that has racing experience for advice. OPM has helped me before, and I've received lots of help from katman, Chet, David Spillman and others. Data aquisition would be invaluable here. And you could get a known fast driver with experience in RWD to take the car out and give you feedback.

Tom Donnelly