Yup. 1/64th ply. Not the cheapest way to go but the thinnest I figured. Since those pictures were taken the wings are done with the sheeting as is the fusealage. I have enlarged the elevators and rudder. About the only thing left to do is finish straightening the ailerons. They were warped. About done with that though. Then start on attaching the wing and control surfaces without glue to fit them properly.
The balsa sheeting on the inner part of the wing I recessed a little with sand paper to lay the plywood into then blended it in with sand paper.
I will get some pictures of it with the finished sheeting.
I also enlarged the F2 and tank tray just enough to allow a Dubro 16 oz. tank to slide thru. Then I built doublers for the weakened parts to bring the strength back. I already had a 16 oz. in my old 4* and wanted to stay with it. It had a removable raised tank cover. Which worked nice as I could inspect my fuel level or tank components at any time.
And I put a true fiberglass cloth with epoxy over the wing joit.