All have made good points, but there is another- liability. Even something as bulletproof as an adapter plate has a liability factor. There will eventually be an idiot who doesn't tighten his bolts enough, causing his tranny to separate and drop out. Who will he go after? You. Better have good insurance, which will require lots of testing and documentation. There is always someone just waiting for another reason to sue, whether you are at fault or not.
Jim
Jim