I'm about half done converting an old Bb Elkhart trumpet to C, but I need some input. I've shortened the leadpipe & bell, and am quite happy with the results - tuning and intonation are pretty good. Now it's time to do the valve slides. Any thoughts on a good way to calculate how much to shorten them? By math it should be about 12%, but I'm not sure. Garry ps Yes, I know this is a crazy project, and I don't expect much. I am a professional tech though, so the mechanics of it are no problem. It's the math I'm not sure about!