I've tried to get some info from nitro planes about securing the top wing panels to the top center section. After the second email, they referred me to this forum. I ran into the same problems as most of the posters. I glued the tail feathers as well as using the screws. I usually toss all the metric screws into a draw and use sae sockets so when it came to mounting the cabanes, I had plenty of slightly longer screws which enabled me to get the lock nuts to thread all the way through. I decided that when I can get the tubes through the top wing and center panel so that they fit well, (there's about a 1/16 gap right now) I'm going to smear some epoxy on the joints where the tubes go in and make it a one piece wing. At that poing I'll have to depend on the flying wires to hold it all together. I have an OS120 pumper in the nose.
Al Burman