Don, what works best for me when joining fuselage halves is to do it right over the top view on the plans. If that's not available, or it's a scratch build, etc., a centerline drawn on chart paper will do. Next, cut all of the crossmembers, and assuming the fuselage is supposed to be square, cut them in pairs. Make sure they are the same length!!! If one is a bit short, save it for the next shorter piece, and cut a new one. Then, get a set of squares together. They can be wood, styrofoam, shelf supports, old TV sets, anything that is 90 deg. They get fastened to your board, and you can use rubberbands or double sided tape to hold the fuselage halves while you are gluing. I'd do no more than two stations (4 crossmembers) at first, and let that set till the glue is dry. Then proceed with the rest.

I know I'm making this task sound like it's a big deal, and I apologise if I'm insulting anyone with basic stuff, but personally, I've always had a hard time getting a straight built-up fuselage, and this method works pretty well, peanut scale to 1/3 scale. Hope this helps!

John