Not to be rude, but if one intends to sell them; what detriment is there in them splitting? Couldn't you sell two smaller ones for more than you could get for one on a piece of rock? Not to mention you have to rip apart your reef to get at them. BTAs do not typically attach to the surface of a rock. They look for a crevice to wedge their foot into.
Fishyness,
Where are you? Maybe a local would be willing to help you remove them if you gave them a good deal on them....