[767Jockey]

I have a Contemporary with a Jag rear. The car has non ride height adjustable Koni's in the rear, and the springs were 11" high, 350 rate. It rides higher than I'd like. Jeff's rode the same way, and he put in 10" high, 250 rate. The height is perfect, however he occasionally rubs tire to fender. I was thinking of either going to 10" 275 rate, or 10" 225 - 475 variable rate springs. Questions I have are:
What's more responsible for the ride height change, the spring height reduction or the reduction in rate?

Is there a downside to ride or handling in using the variable rate springs?
For those of you who have a good understanding of these things (I certainly don't) what do you recommend that I do?
Thanks.