When I called Redline, they recommended D4 for T5's, even if in a hot climate (I wanted to see if MTL would fly). The guy I talked to was against it, saying D4 was created just for this application. Makes sense to me, though some guys do run the thicker MTL.
I do mine the same way Steve does. A stanger recently was doing his rear end fluid (same sort of plug) and lost some skin. Try not to use a wobble fitting or a button-releasing ratchet in the plug (it keeps the 4 sided male dealie in the wrench from seating, and it can slip out). And wear mechanics gloves. I push on the wrenches' head (pushing it into the plug, to help keep it from slipping - all my ratchets have button disconnects) with one hand. If the plug wont come out, I hit the wrench with a fist, which has an impact effect.
Good luck.