Some very interesting observations after cleaning from race day.

I now know why Tamiya M05's have so much understeer. Here are a couple of pics that show the differences between the M05 and an FWD chassis that follows a more "conventional" approach to steering and adjustment.

The first pic is of an M05 S-Spec's front end. This shows where the problem lies in regard to it's understeer. The caster is molded into the chassis halves at approx. 4 degrees, and is non-adjustable. In "standard" on-road chassis, caster would be adjusted at the knuckles, but in this case, the knuckles are set at 90 degrees, and caster is achieved through the angle of the lower suspension mounts. This is also called "kickup." The kickup in this case is why the M05 understeers, and the understeer only gets worse with acceleration.

Pic 2 shows an ABC Hobby Grid's front end. Notice here that the suspension arms are conventionally mounted, and caster adjustment is done through moving the lower suspension arms forward or aft. In this case, the most caster that can be adjusted into the Grid's front end is 3 degrees. The minimum of one degree is adjusted here. Notice also, the use of shims to raise the rear suspension pin mount to give 1 degree of "anti-dive," which allows for more on-power steering. There is also 1 degree of "pro squat" adjusted in the rear arms, as well. This gives the Grid exceptional steering, with much reduced understeer. It is this reason that makes the Grid so much faster in corners than the M05.

I only wish Tamiya would correct this "deficiency" in the M05. It is still a favorite of mine, and with the Grid, will keep me into "M" class chassis for the forseeable future, regardless of it's "quirks."
I just thought I better mention these differences, so anyone considering an "M" class chassis know what they're getting.