This is the ring guide on the router. I had to off-set the jig below by 3/32" to allow for the distance between the guide and the cutter.

I made the rib templates out of 1/2" MDF, using a router with a ring guide. There would be 6 rib templates in all: upper wing full, upper wing less aileron, upper wing end, and the same for the lower wing. However, I can get away with making 4 templates - the full rib templates can be re-cut to make the less-aileron templates after the full ribs have been made.

1" strips of 1/2" MDF were cut and stapled around each aperture. I initially cut out a lot of the surplus with a jigsaw - less work for the router bit.

Here is a finished upper wing template.