Hi Grant
looking at the plans the rudder is 60mm deep and 13mm wide.
The turn fin is 35mm deep and 18mm wide.
Going on about the same size boat on the Hobbyking site.
The Ariane 2(930mm) has a 3660-2075kv(water cooled)brushless motor with a 125Ammp water cooled ESC running a 5000mah 4S Lipo battery.
No prop size given sadly.
Rudder servo 3KG+..
They have a good number of drive unit with flex drive cables.
With that powered motor I go 5mm flex drive.
Canabus