[xlr8tr]

A couple of background questions: does your car have sway bars? How is the handling now: over/understeer?

If you increase the rear springs you will increase oversteer, that you could then adjust out with stiffer front sway bar and/or stiffer front springs.

If your handling is where you want it, increasing both the front AND rear springs by the same percentage should stiffen the ride but leave your handling under/oversteer unchanged. I haven't played with it a ton, but certainly form my lmited experience you can raise OVERALL spring rate quite a bit without changing ride harshness as much as you might think. If you are just adding spring to one end, you would have to do that in much smaller chunks.

For example: My cobra was VERY soft, I raised springs 50% both front and rear: handling balance stayed as it was prior to the change, ride stiffness went well up, but not nearly as much as I thought. For example, front springs were 350 lbs/inch, new ones are 525.

I like the idea of trying to get a bit more anti-squat if you can. Not sure what other geometry issues that might cause (i.e. toe in/toe out change under compression etc).