I am curious about the 1/8th diffs, but I love running a spool in the rear and wouldn't want to loose that option. Are the diffs you're talking about in the RC Monster store?
As far as the Kongs go, I simply love their size, appearance, and performance climbing/bashing. I know I'm asking a lot running these tires with this kind of low end grunt, but I'm sure you can identify with wanting the best of both worlds from your RC's.
I have already loosened my slipper a bit and hope this helps.