Heres another method where the left/right balsa sheets are laminated on a 1/64" ply center section. The 1/64 has 'pockets' cut out of them spaced & sized to accept those mylar ca glue-in type hinges. After the shaping the profile, the flying surface is cut away exposing the pockets (the 1/64 is the right thicknes to accept the ca hinge). The hinges are glued in place & are perfectly centered, no messin around. The 1/64 also helps define the c/l for those oh-so important razor blade trailing edges. I like everything about this method except the extra weight so I ended up making lightening holes.