All things remaining constant, going to smaller tires would mean you need less bump stop. If their purpose is to prevent tire rubbing, like Red Chili said. If you aren't rubbing 35's, you shurely won't rub 33's.. IMO. only change the BS if you have more upward travel in your shocks, won't interfere other components, etc. otherwise keep them the same.
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 06 TW200, 89 TW200, 09 TTR125, 07 TTR90, 07 CRF50