After several weeks of occasionally working on the ASR, it suddenly was ready for testing. As we don't have a bath (just a shower), I wasn't able to make sure it floated, remained upright and level, and didn't leak.
So, battery in, superstructure on hull, and carefully placed it in the water at the Oxford club's water in Hinksey Park. Against all expectations (sorry, Ron Dean!) it stayed upright and level and very close to the water line.
Battery plugged in, steering and motor appeared to respond, so back in the water and the throttle tentatively opened - and off she went. Within a minute I was confidently making full throttle passes inches from the concrete bank.
The ASR was on the water for over two hours, greatly admired by the other club members present (and by a few passers by), at the end of which the battery still had 55% of its charge left in it. The boat was also completely dry inside, not a single drop of water or even a damp patch.
Thirty years since I last had a Deans Marine fast launch, and it brought back so many memories of my Motor Gun Boat - a new kit for which is my next project!
Ron might want to cover his eyes at this point, as I will list the drive train and radio used. Motor is a 2836 1000kv brushless out runner, battery is a 2900 mah 2 cell lipo, and the radio is a Fly Sky car radio (steering wheel and trigger throttle). I wasn't sure about using the radio, but it worked out very well and was intuitive to use.