Built one for a mate in about 89, added the wing keel bulb from another unknown Robbe yacht, recently did a refurb (longer boom and a new set of Nylet sails) the longer boom was I believe from the Atlantis courtesy of westbourne models. Mate is a full size yachting type and wanted a more scale realistic sail.
The motor sat in a framework, surrounded by a wooden 'floor' that held esc, rx and battery, lighting control and sail arm servo. (Accessible through the remove able cockpit floor, )motor was a 540 I believe with a two blade prop of around 30mm.
Of course I've been asleep since I did all that, so I might be a bit out.
I will contact aforementioned mate tomorrow to see if he still has the drawings.