[1retired06]

After you pull your flap back, first concern I would have is how much of the plywood is actually damaged. If small, after you dry it out, apply one of multiple products at Home Depot for restoring rotted wood. I used on a rotting window sill in one of my houses, and after sanding and painting, you could not tell there was a patch. Eternabond tape would work fine for reinstalling the flap. IF the moisture has spread throughout a significant area, you have a major repair on your hands.