However, I read your topic with interest and curiosity. One thing that came to mind was the trend (I guess?) to "scoop" out rotors on some tubas. I remember hearing and reading about folks doing this on Cerveny tubas in particular. I do not know the actual measure of the increased bore size that came with scooping out your rotors, but it always struck me as increasing the bore size, but only in a very small way. I do not know what the results were or how widespread the practice really was, but short of full-on frankentuba builds and valve set swaps, this is about all I can think of along these lines.
Thoughts/comments?
