Hey D thanks for the very detailed reply, I hope the illustration did not take you too long!
I figured that was how you did it, so nice to have that confirmed. As I'm a lazy so-and-so and want to speed the build process up, I'm looking to use laser cutting for the templates. Unfortunately this means I wouldn't be able to use the DXF's you've posted as the laser cuts every line it sees, so of course there would be lots of 1/4'd templates as they are at the moment.
Because of this I need to pursue the centre reference rod/s idea. I also need to design in the EDF (or EDF's - plural) and cabin etc. Given this would you mind sharing your SKP file? I would need to brush up on my Sketchup skills but in the long run the more this is designed on a PC the less time spent cutting
I would of course share-back the final design with full credit to yourself for all your work in converting this classic plane from 2D to 3D