sdpatt:
There is already a "drain plug" installed in the MTX. I learned it from the SHO NUT MTX video. It is the 13mm shifter interlock bolt on the angled face of the forward, driver side of the transaxle. This bolt drains all but the lowest portions of the differential well. The only caveat with using this bolt is place the shifter in neutral and do not move it until the bolt is replaced. Use Teflon tape on the bolt and torque gently to (about) 12 lb-ft.
After seeing the internals of the transaxle, I strongly advise not drilling into the transaxle casing at the risk of creating aluminum shavings inside the case that cannot be trapped by the magnet. These loose metallic shavings can cause more damage to the gear train and its oiling system than almost any transmission fluid. Be forewarned.