I have a Marvin Miller Anderson Spitfire 65 that I put about 2 hours running time on, and really was not impressed with the compression I was getting. I had picked up a set of Franks rings for the spitfire a few years ago at VSC, and so I scuffed up the cyl. a little with 400 grit wet or dry with oil, and replaced the rings with Franks. After about an hours running it has super compression, and runs superbly. Thanks Frank. Your rings have to be the ultimate.