'Fraid he's got you there Bandit....
The plywood won't bend that way.
For the front you could sand in a smooth rounded curve and then laminate something like 2 layers of 1/32 ply that curve around the center bend. On the rear you could make a spruce joiner that is sanded into a long triangle shape that matches the spar angle. With the ply on the forward side and the spruce on the rear it should hold up just fine.
You can build in the rear joiner on the board but make your center ribs in two parts and leave out the front until you can lift the joined wing up and sand the smooth long radius curve into the front face and laminate the two layer joiner onto the front and then trim it and insert the forward parts of the ribs.