I've got 350 lb/in F, 400 lb/in rear GC's on my Si, and that is stiff as shit for street driving. I can't imagine 450/500 is too comfortable on the road. Should be great for the track though. What shocks are you using? I'm on Koni Sports (yellows) with the stock (although trimmed) bumpstops, and there's no second guessing when you bottom it out. It feels like the front end of the car is on a pogo-stick for a second or so. I didn't lower my car too aggressively. There's about 3/4" from tire to fender, and it will still bottom out in a real tight corner if I'm on the brakes too late. If you're bottom out while on the gas, that's odd, and you're probably too low.

Rotation (or lack thereof) can be controlled by too many factors. What rear lower sway bar are you using? I've got the adjustable Comptech unit on it's stiffest setting, and I still have to lift to get the car to rotate. Tire pressure and alignment are big parts of the equation too. The simple fact is FWD Hondas don't like to rotate, and when they do, you're riding a fine line between gripping, and a complete spin out.

Just sell your soul and go RWD... I did . One of the best choices I've made. Throttle induced oversteer is soooo much more controlable and enjoyable than lift-oversteer. Now I've just gotta sell the Civic.