I'm half way through mine right now. I was also surprised that GP went through the troubles of gluing a piece of wood for the aileron control horn, but they didn't do anything for the backplate. I plan to cut open the covering like you said. I already have a roll of cub yellow monocote from another project, so I've got plenty to recover these and other places, like the wing center, where I cut open to fiberglass the wing joint.