Hey Volfy I used a tube in tube assembly about like you'll find in a big bingo.I do not use any dihedral and I use a ply ribs on inboard and outboard ends of the tube sockets.The sheeting goes on next to the inboard rib only.The ribs in between the ply ones can be regular ones.If you use a 18" aluminum tube then your phenolic ones that goes it the wing panels will be 9" long each that is how long your sheeting will be.Finally use a extra balsa block in the wing just ahead of main spar under the sheeting.You will now have 2 places to attach your bolts after you drill thru the balsa block and install additional mounts in the fuse. then top it off with thin aluminum straps with holes at either end to prevent wing from spreading apart at hi G maneuvers.Good luck let me know how they turn out.