I agree with Denny, but, I'd say JC's kit is a below average fit.
The JC kit is actually inadequate. Without a piece of coir or a heavy piece of carpet, the coils will caress your rump.
See if you can find a local uphosterer. I had a hard time finding one who would talk with me. I eventually found an older fellow in a small town/village nearby. He did an excellent job.
