To maintain ride height and have the spring secure itself in the stock strut you will need to cut approx. 0.75 inches off the top AND bottom, (making a 10.75 inch long 200#/inch spring). The I.D. of 2.5 inches works but don't go narrower. The top spring hat rotates freely so it does not matter exactly where you cut the spring but it needs to be cut top and bottom to to create a step or ledge in the spring so it locks itself in place. Not sure if I explained that clearly.
After many months and some pretty long road trips with two passengers these springs are working well. No detectable noise or hardware issues and I would recommend them for the out of warranty tinkerer.