Too bad ole' Bix left us so early. You sound like you know what you're doing. Just for edification about phonographs--no the diameter of the idler wheel doesn't factor in, but its condition does. It either gets hard and slick, or it gets gooey. So I have to send off idler wheels and Rochelle salt cartridges for rebuilding. I re-cap the chassis, check and/or replace tubes, and put it up on the Hickok for re-alignment. Typical procedure.