A really nice build. You cousins across the pond are soooo much ahead of us here in the States. No one here would even dream of tackling such a project.
I do wonder about your propulsion system. I would tend to lean toward a geared system, simply to reduce the current load on the motor, but with the size that you are working, I guess a few car batteries would be more than enough power supply, leaving you to put in a large slow turning motor.
There is a fellow down the road from me that converted a training hull into a ride along and he uses an electric trolling motor for power. His craft is 16 feet and the trolling motor gives him well over scale speed and great control.
Beautifully done project! And I thought my 1/4 scale boats were big.
Jonathan