Are polyurethane spring isolators thicker than the stock rubber ones. I've read that they raise the ride height by 1/2 inch. Is this because they are new, or because they are thicker than the stock ones? The reason I ask is because I have a set of FRPP "B" springs and they only lower the car 7/8 inch in the front-which is perfect for me- but I can't have isolators take 1/2 inch away from me.