Like Jim said, we race our mini's with plenty of traction on the front (S-grips all around, softer springs in the front). Once you have "too much" traction, CA glue becomes your friend. Personally, i put CA on the outer edge of the outside tread and then proceed to put CA on the top of the outside tread blocks.

If you are going to use the original planetary diff and stiffen it up (shims, shewing gum, etc etc), it is reccomended to switch to hard metal outdrives.