Just make SURE that you don't cover any adjacent pins when you do the taping. That would be BAD!!
If it doesn't work w/ the B21 (Forces 100Mhz Bus) and the A121, A119, B119 (Forces 2.2v) taped, you're out of luck. You kinda have to get lucky to get 500 Mhz out of one of those though, but it's worth a shot.