[Wad Cutter]

Once again I find myself in a with a problem. I'm trying to build the FG shuttle. When I try to seat the main body(fuselage)onto the wings, there is a gap between the two. Right now my only idea is to shim the the gap. What am I doing wrong? A day will come when I can build a paper model and not have one of these problems. Does anyone have any ideas? Has any one else built this shuttle? Thank you for any and all help offered. wc