Since river testing was inconclusive, this morning I took the boat along to Hartsholme Park, where the good folk of HEMBC gave it the once-over and pronounced it seaworthy.
All in all I am well pleased with how it runs. It has a decent turn of speed - more than I thought it would have with the stock motors on 7.2V - and it handles well, turning smoothly at full throttle with no fuss or bother.
The only thing I am wondering about is the tendency for the bow to bob up and down when going at full chat. It isn't excessive, so I'm not going to lose sleep over it, but do y'all think this is due to a CoG issue, or will trim tabs help?
Anyway, here is a photo of it underway:
Next step is to strip it of its gubbins, give it a decent paint job, reinstall the gubbins and add some scale accessories. Then the boat will be done, and I'll turn my attention to the trailer.