The 500 bump steer mod is to install a 0.25 inch shim on the lower ball joint, same as the 250. Also move the inner tie rod end up 0.2 inches with washers between the tie rod end and the steering stem. Then reset the toe in to a quarter inch. That's what I did based on information from QRHQ. Seems good bit then I didn't ride the Zilla without the mod.