re: Covering the rib cage with 1/4 " plywood

It would have gone much easier if you had bent the plywood on it’s other axis with the surface grain going across the curve and only the centre ply(s) in flex.
I’ve bent a lot of 1/4" pw and it’s just way easier that way. It’s very easy to scarf edge to edge to get more that the four feet if you need it.

But it seems to be done now so on to the next step.

Keep us posted. You are a brave adventurer Abbas.