Richard, thanks. When I got back into tuba playing, I borrowed several mouthpieces, doing exactly what Ken suggested - taking notes. Then I had a long conversation with Matt Walters at Dillon Music about my playing, my tuba, the ensembles, the repertoire, and especially the weak points. He made his recommendation. His mouthpiece man, Vladimir, altered the contour of the rim a little bit for my personal preference. It is now the mouthpiece I play. Sure, I have a couple others, but by being careful up front, I have saved thousands of $$ on the safari and avoided the "mouthpiece du jour" rut that I see so many brass players fall into.
The mouthpieces have specs as well. Being long distance, I could tell Matt I like the way "X" mouthpiece feels, but I like the tone of "Y" better, and the response of "Z." Because the specs of the mouthpieces were available, he was able to help translate my subjective impressions and observations into objective criteria to help me choose the proper mouthpiece for me out of that universe.
I guess that's the bottom line with the string rants, and I've used up too much of Ken's bandwidth already. Thanks, Ken.