I too am building a 4 Star 40, and just got done glueing the 2 wing halves together. I had a simular problem with having a gap on top of about 1/16th of an inch wide. I used 15 minute epoxy on the dihedral brace but for the gap between the main wing spares, I used elmers probond polyurethane glue. The amazing thing about this glue as it's setting up it actually expands and fills in gaps. ( You can watch it expand!) It appears to be very strong and sandable. I hear gorrilla glue is simular.