Alex, what a superb job you have done so far! I am truly impressed with your ingenuity to replicate the crank. You are putting me to shame, I can't even find the motivation this week to fix the brake cables on my BSA! (The fresh snow and ice outside doesn't help either, my garage isn't heated)
One thing intrigues me about the paint on my BSA however. You mention black primer and the green top coat. My bicycle seems to have the turd brown colour inbetween the primer and the green
This only applies to the frame/forks/handle bars/crank. The brake calipers seem to be only green on black. BTW, my pedals show evidence of paint on the rods. It is likely they were painted at the factory, but the paint would very quickly get worn off due to use and there purposeful sliding in and out of the crank arm.
Since mine is the only unrestored BSA Airborne cycle I have seen up close, I can't explain the odd paint or have any reference to compare too? Mine is serial number R14015. Most of the BSA's I see in photos are much more green colour than mine. Mine only has a very light coating almost a "mist" of green over the brown?
Here is a photo of the crank on my bike (I had removed the rear wheel and chain for maintenance when this picture was taken)... shows how accurate your build is and my odd paint job. The brown shows clearly where the green has worn away from contact with boots and trousers. Also a shot of the BSA logo/decal on the downtube, shows chips that reveal the primer, the brown and the top coat of green.
(Alex, I am also assuming you received the photos I emailed you the other day?)