FYI, I just opened the diff on my XT8 (ripped the shocktower off the bulkhead doing repeated stupid jumps
) and noticed that the pinion has two shims between the pinion and the bearing (pushing it closer to the diff). The gears look in very good condition considering the punishment I put this truggy through, and it wasn't new when I got it (got it from a member here).
I know you came up with a different solution, but just thought I'd toss how mine is set up for kicks.