Thanks for the advice. I thought it wouldn't be as simple as just gluing the planks on (and don't worry, I wouldn't have attempted this until I was more or less certain that it would work... it's some time before the model will get to this stage anyway, I'm still working on the radio/motor installation and ballast)
The model is definitely skinned with wood (ply, about 1.5mm thick), its interior surface is completely unpainted. As I mentioned, though, it appears to have some sort of coating on the outside surface (polyester resin?), which is a pale greyish-white colour, under the paint.
I should have made this clearer in my original post - I wasn't intending to glue the planks straight onto the painted surface, I planned to sand as the paint down as much as possible to the treated surface underneath, then glue the planks to this. Assuming the wood is treated with polyester resin, will superglue form a strong bond with this?
I was also considering painting the interior surfaces of the wood with sanding sealer or possibly Cascamite wood glue to add strength and prevent water damage. Would this be helpful, or would it be counter-productive in making the (currently quite flexible) thin ply skin stiffer and more brittle?)