I just went through part of this operation when I changed plinths on my LP12. The WTA arm is a royal pain to work with. Getting the silicone out of the cup was an exercise in frustration, as not all will be removed from the cup, leaving a nice mess. I did it with a syringe used to baste with, but it is not easy. The silicone liquid will spill everywhere, and it is a pain to clean up. This, IMO, is one of the biggest issues with ownership of the WTA. If I could source an arm that was more interesting sonically on the LP12, for a reasonable price, the WTA would be gone, because of this sole issue~
If you do mount your WTA on the LP12, I think you will be pleasantly surprised how great it sounds...and works with the old fruit box.