(Send on behalf of Bill Akins)
I made this motor mount for my wetsub out of an old aluminum stop sign.
Cut with a scroll saw, then paint stripper applied, then it was
bent by hand over a 4 inch pipe for the main horseshoe bend, then carefully
bent between two metal angle irons on a vice to conform to the sub's curvature.
Slots were cut for the hose style clamps that holds the motor and another
slot cut for the minnkota's little rudder you see sticking up. Only one clamp
holding motor in picture. Will have two and be painted when finished. 
Stainless bolts, washers and lock washers holds it to hull. 
Everything was done by hand to "that looks about right" specs.
Very sturdy and works great.
Bill Akins.