One of my tests for a great playing tenor is the ease with which I can play a subtone G1 followed by a subtone Bb1 without difficulty. There is a passage in "Don't Blame Me" where I like to play that sequence. Specifically the 1st 2 notes of the 5th measure or elsewhere where the melody repeats that phrase.
Al, I missed this post when it first appeared. That's a great test for the low register. At least it's more musical than what I've been using to test my repairs. I'm going to start using it, and for the REAL acid test, 1/2 step higher ought to show whether I got everything right.