In the event fitting the motors proves to be less hassle than fitting the tins, and here's the proof. I'll suspend the motors so that the props are largely protected from damage and the four of them will be pitched about the C of G, allowing the boat to be flown in free air as a quadcopter but also in ground-effect like a hovercraft. In this last case propulsion may be provided by the cruise-motors at the rear, using less energy in view of the fact that the lift-motors then need make fewer adjustments to RPM.
Am off now for a well-deserved tuna sandwich...
