yep, your hull, Phil. The stuff a transom is subjected to with a surface drive mudmotor are much more than what an outboard normally does (IMO), that any 'extension' type of mount gives some added leverage to the forces applied.. I'm not saying that the good looking work you've done wouldn't work with something in the 12hp/110# range, either....but if you step up to the 165# class of shorttails, we're talking the 23hp+ motors, and exponentially more torque and speed to subject the transom and hull to with impacts, etc. It might never fail, but if it did, it might also rip the entire stern off.