Front/Rear belt fix
Shave off a half moon portion in the plastic part (mid block and front) where the diff's bearings are inserted using a dremel, just a tad. Then inserts metal strip from a metal fastener cut half to quarter circle on the area not shaved to move the bearing just a bit toward the other pulley making the belt looser than in its original position.
Others said they leave the rear alone and let it break-in itself. Front they put thin washers in the mid-block tilting the block forward to free up the belt.