The alumacraft river runners had a high transom for an outboard jet. Maybe you could pattern your transom after them. No wood in them. Not sure what you have. River runners were sponges because alumacraft foamed into the strakes w/o a floor. Had to rebuild mine. But for your needs their...
These threads are completely wrong. The threads are old so I am not going to elaborate on the problems and the cures, unless someone still needs to know.