I had read from other builders' experiences that the leading edge can deform a little over time and using insulation foam between each leading edge rib provides additional support. So I went that option using Titebond III. The 0.8mm plywood will be glued and stapled one side at a time just as was done on the ailerons. Just held temporarily in place on guide nails in the top of the spar. Titebond III on the opposite side the following day and way too many staples to count will hold everything snugly until the glue has dried.
