your thinking too hard. either sand the two wings so they fit perfect (not nessiary) or just glue them together
this isnt machine class where everything has to fit perfectly, think kindergarden glueing session unless you plan on crazy overpowering it you will never have that glue joint fail. the expoxy is so strong compared to the foam around it the joint failing is the least of your worries, even if its only half glued

my point is dont worry about it, just glue the dang thing together