I often make jigs for assembling biplanes myself out of scrap material. One jig I frequently make is a dummy top wing from acrylic or other transparent plastic. I measure carefully the holes in the top wing, and transfer the measurements to the transparent wing. This allows me to see the struts fitting into the holes much easier than with the actual wing. I use this dummy wing to glue on the struts and adjust until the dummy wing sits correctly. I allow the struts to set up completely, before replacing the dummy wing with the actual wing. I do not, of course, apply any glue to where the struts go into the holes on the dummy wing. I make other jigs, say the ones to set dihedral on lower wings, from inexpensive particle board. I always keep scraps of that stuff around just for making jigs.