I realize not everyone has FB or is a member of the group it was posted in, so I took some screenshots and saved the pics. Being sold by Christopher Messinger for $12,500.
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Either leave it alone (what the hell's wrong with BBb anyway, if a horn plays great?), or re-taper, or make suitable bows from scratch which won't be such an acoustical nightmare.
I see what you're saying now—the bows are pretty starkly different sizes because of the cut, right? I thought you were more talking about the way the tuba was wrapped.
Pure luck then. And what a shame for the horns he turned into junk.
I hope it plays well, but I have no desire to own it. Well, if I could buy only the bell, that might be interesting.
Search through and find Wade's series on rebuilding his Rusk-cut Holton 345 and what he did to make it more to his liking. This would give you a view on how Mr. Rusk shortened up a BBb to CC.
The way Rusk did it (cutting and then telescoping ends of bows inside each other) creates a stairstep interior wall which is not conducive to formation of standing waves inside the instrument. A smooth interior bore is what makes that possible.
He was (one of?) the first people to really take on the "cut a 6/4 to CC" projects, and to any sort of scale as well. My impression is that his tubas were generally well-regarded at the time, because they filled a gap in availability that otherwise had no options. That is, there really weren't any other 6/4 CC options (or very, very few), so by default, his was well regarded because it existed.