I've hoisted the second float half to the roof.
Backed off the screws holding the battens to the mould (after numbering them so I know where each one goes). Lifted the battens up and reversed all the frames and then screwed the battens back in the mirrored position. So now I can start cutting foam to make the other side of the two floats.
Leaving all the screws in and keeping the battens in the same relative position saved me a heap of work.