I was able to get my 40/60 weight bias without adding any more weight than the C and D block, some minor dremel work and the XB4 aluminum rear hubs and a 25g weight plate under the battery.
I dremeled 1mm off the front of the rear a-arms to shim them forward.
And then added the xb4 or XB2 hubs to gain an additionall 2mm.
The xb4 hubs move the driveshafts approx 2mm in torwards the diff and would bottom out at full compression so I had to widen the track width at the C and D block to offset the driveshat plunge.
FYI, it was confirmed that the XB2 aluminum hubs offer the same additional 2mm of shimming that the XB4 hubs have, I had the XB4 hubs on hand so I used them but will be getting the XB2 aluminum hubs...