I don't have an answer, but could I ask what piece? Mainly I'm curious if the Forrests style one would even work—I've had at least 1 (maybe 2; haven't think a bit to remember) not-that-obscure pieces where even the one with the sleeve wouldn't work, and one more where it was really hard to do the switch. I'm wishing I had one keyed to Bb ever more. I've looked into actually adding the keywork, but, although I could probably convince someone to do it, no one is really happy and just says "get a new one." At first level, technically, it doesn't look that hard, but I guess the Bb rod doesn't come assembled and is difficult to get the right "feel" in.