Jim,
I have had no issues with my MO5 V2 with the gears or motor screws. I have used what was indicated in the instructions. I also use the alloy thin plate to prevent dirt getting into the gearbox and motor. I put the screws through first, place the alloy plate then screw the motor in, using the spacers on the motor screws.
My gearbox is nice and smooth. I am using the standard steel shafts with the normal white gears, with the TOP racing oil gear diff with 300 000 weight oil. This works well and still gives good forward bite and steering.
For those who have complained about a lack of rear end grip, perhaps you need to consider smaller hexes, 4 mm or 5mm and making sure not to have to much negative rear camber. I find 1.5 degrees of rear camber seems to work best for the tyre combination I run, which is adjusted by the changing the spacer width on the rear upper link.
Later,
Calvin