Very nice post you got there. In regard to yonex grip size, i shrunk down my VT80 grip from G4 to somewhere G6 or something. It changes the BP considerably and i hope it wouldn't suffer from grip-breakage. Also, i notice that Yonex (along with Victor, Kumpoo, Gosen, etc) stuck a little piece of hard "bullet-alike" into the center of the grip, tightly screwed. Some use like 3-7cm rubber bullet and some use plastic. Try to take 'em off your grip and there you have the headheavy monster. Shrink down the grip few mm off and you get more headheavier racket. (Tested on Yonex VT80 3UG4 became→4UG6)
