I think you guys are into this idea because of the ease of steering, and the added manuverability. Its a great concept but my suggestion would be to have a side mount, near the front. That way it leaves you more room in front for fishing, and you dont have a prop quite so close to your feet
Basically all you need is a board that overhangs one side, and is strapped down securely, that would be the best way IMO.