[Carpo]

Jigs are over-rated. I use VHS video tapes and CD covers to square everything up and support the structures as the glue dries.
I also use clear acetate film from OHP slides to set the correct wing stagger.
It is a rather complicated idea to explain but simple to do.
I place clear acetate over the scale drawings of the aircraft.
I mark on this sheet, the curvature of the bottom of the top wing and the curvature of the top of the bottom wing.
I also mark the attachment points of the struts.
THEN I cut this sheet to leave a void for the top and bottom wings to fit into. Make two of these.
The resultant shapes are something like an italicised letter H.
Then, after the bottom wing is fitted to the fuselage, I place this jig on the lower wing.
I glue the interplane struts in place and use the template to align them to the correct angle.
I tack the struts to the template with masking tape and allow the whole thing to dry overnight.
Make sure the lateral alignment of the struts is correct (usually perpendicular)
Repeat this for all of the struts.
Once all is set up, you can drop the top wing onto the structure.
Glue and then remove these templates.
Hope that makes sense.
Carpo