Revo V3 Hybrids question

[Urgeoner]

Is there a way to make the v3 diff smooth as butter? both of mine spin pretty smooth 3/4 the way, then they kinda get a little rough the other 1/4 of the way. The actual differential are fine, but I'm talking about the mesh of the ring gears and the input bevel gear.. I'm thinking it's the ring gear being slightly tight or loose which causes it to warp at 1/4 of the way, so is there a method to tightening the four screws that hold the ring gear on?
It seems the more I loosen the 4 screws, the easier it turns, but then the ring gear isn't tight and not completely seated against the plastic diff cup...it's frustrating can someone help out?

Also, what mugen, AE and other diff options can these cases support?