BDH visited the factory last week and picked up a number of GMU11 mounts. The factory advised the best position for the mount, which is very tricky for me, as I have covered in the rear skins of the aircraft. I made a jig to allow me to drill the rivet holes in the correct position on the rib 4 flange as I was unable to see very well inside the fuselage. I found that it was much easier to drill the rivet holes on rib 4 flange with the aircraft upside down and reaching through the luggage compartment with the floor removed.