Found a better way to rivet the structure on the firewall, Using clamps I've clamped the frame to a table top in the vertical plain. This allows a rivet gun on one side and bucking bar on the other. The quality of the flush side is superior to the back rivet method. I'm going to drill out and replace many of the rivets I've put in just to get the better flush finish. This will take some time but I think its worth it.
