I built a Rapier during Covid, based on Cornwalls plan. The large mtronics brushless motor fits low down in the front, although I've had trouble with the speed controller when fitted to a 3cell lipo. Its quit happy on 2cell. To fit everything in, the rear foil is horizontal under the hull with the prop underneath, and the rudder behind that. I ignored the aileron set up, as too fragile, but have had to enlarge the rudder. I've used 1in aluminium door threshold for the foils, and adjusted the angle by washers. So far so good. Good luck

Thanks all that replied, the info and articles were really helpful. Almost finished my current model (dolls house for my granddaughter) then will start on the Rapier, will post a few pictures and comments as the build progresses...

This is cool…

http://www.foils.org/wp-content/uploads/2017/09/Radio-Controlled-RC-Model-Hydrofoils-Power-Sail-1.pdf

You’ve probably already seen this too…
https://www.cornwallmodelboats.co.uk/acatalog/mar2392.html

There’s a nice article here. 😊

https://www.modelboats.co.uk/1292/model-boats-december-2021/