So I think I found out why my M05v2R was pulling left when accelerating. I checked the corner weights using 4 small scales and found that the front right and rear left wheels were carrying a lot more weight than the opposing ones. I checked the preload of the shocks, and the corners carrying the most weight were set quite a bit shorter than the others, yet those wheels touched the ground first when testing droop.
I suspected the chassis was twisted, so I loosened all the screws connecting the front half to the rear half of the chassis, gave it a wiggle, then tightened it back up. The corner weights balance pretty close to even now with roughly equal length shocks. Hopefully it runs straighter next time I take it for a spin.