Welcome to the forum. You sound like you belong here.
Fenix TK75 and a Sunwayman D40A? Damn, you started out well. I bought a ton of junk lights before finally bought those two great lights. You're a very discerning buyer. Congrats.
Have you seen RaceR86's mod thread for the TK75 here? With a very simple resistor mod you can take turbo from 2.88 amps per emitter to 3.65 amps.