I use 60wt in the shocks and chest high it does not bottom out but it still handles great. My son has already done some pretty big jumps and it jumps awsome.

As for the diffs the front and rear are fine but still no wheelies. I am up to 60wt in the center and the front tires dont baloon as much but still spin faster than rear. Im going to try 80wt and 100 wt. It will pop the wheels up slightly but then the torque goes to the front and comes back down so Im close. Thats the only downfall with a center diff opposed to a transmission.
I will let you guys know what weight will work to get these wheels up.