I'm not looking for any "magic bullet". I am telling you that on 5different Crowns or Speeds I have calibrated--that I have successfully gotten the Kalarts to be so absolutely dead-on within less than 1/8 of an inch of in agreement with the groundglass from 4 feet to 50 feet. I've calibrated these things to where you don't need to use the GG and a magnifier. In other words--perfect. But when I remove the 135 Optar and put on the 135 Schneider, it's off by a good bit. Bothe 135's are marked 135, but they are not exactly. This means that since the top-mounted Graphic finders that use cams cannot possibly be so dead-perfect. The cams are for their marked focal-length lenses. Yes, I can make cams, and yes I am a very meticulous perfectionist worker, but you can sand, file, taper, and labor till you end up in an asylum on a cam and never get it just perfect. The only reason I leaned towards the top-mounted finders is the auto-parallax and the handy push-button beam light. Actually, the top-mounted finders are really plasticy-junky in construction.