Ideally, bumpstops are determined by things other than tire size, like the amount of reverse flex that is acceptable, tie rod/drag link clearance, etc. Nevertheless some folks use them to limit body contact (not the best rationale, but hey, whatever works). Which situation are you in?
Heb Dduw, heb ddim; Duw a digon
I'm that gun-totin', farm-raised, evangelical, pro-environment, OHV ridin'/drivin', Southern civil rights pro-labor Liberal yo' momma told you couldn't possibly exist.