r6banshee

Hey guys im new to the forum. I have a 2001 r6 swapped banshee and I made a +12 swingarm for it. I am using the stock bike exhaust so I don't have much clearance. the problem that I'm having is that with a swingarm extension....obviously there is more leverage resulting in the rear coilover squating more that with a stock swingarm. Is there heavier rate spring available for the stock shock so that im not bottoming out so quickly?