Bought a piece of schedule 40 PVC pipe, 1 5/8 inch outside diameter at the hardware. Clamped this in my bending rig and pushed and pulled on the skin to finally get a decent fit for the bulkheads. Put the tailwheel mount in and was relieved to see the weldment fits well and appears to be parallel to both bulkheads. Should require minimal or no shimming to get a good fit. Spent some time with trial and error fitting of the cutout in the F-779 and the "mouse hole" in the F-712 to get all the parts to fit together better.