[EricH]

6WD "drop center" or "rocker" isn't too hard. The main thing is to get the drop right and the CG right.

The drop shouldn't be very much. 1/16" -1/4" is sort of the "standard" range, with the majority being around 1/8"-3/16". Occasionally, someone has more.

CG is kind of important. You don't really want it dead center, surprisingly enough. This will aggravate the rock, causing undesirable results. Somewhat forward/aft seems to work much better.

Other than that, try different combinations of wheels. Sometimes, that can help performance.