But there is a third kind of plywood. Lite ply is kind of junky with voids and knotholes and is pretty soft stuff. Certainly 5 ply 1/8 is the strongest, and heaviest but I have found it unnecessary in my profiles. Enter Frank Tianos Mighty Lite 3 ply x 3mm. (I think Midwest also has a version of this!) I put this on the outboard fuselage side back over the high point of the wing, and cutting out the area over the maple mm's. As Jim says above, mount the engine lugs on maple, or any type of engine support. (Aluminum, Nylon, or whatever). The inboard fuse gets a shaped and hollowed 1/2 inch balsa tripler. Do not hollow over the wing joint. Note: No plywood here! That's it. Lite, strong, and it absorbs the vibrations. My piped profile Force is over 10-12 years old now and shows no signs of the "aging profile nose"!
W.