I was puzzled for a while on how to make the 2 holes for the fuel pump attach brackets to the stiffener ribs on the floor skin.
The holes are made in the brackets and in the cover but not yet in the floor stiffeners. Since the cover slides in between the stiffeners, there's no way you can matchdrill.
After thinking this over for a while, I came up with a good plan.
I took some stock scrap aluminum angle and clamped it flat on the floor skin and clamped against the floor stiffeners with some vise grips.
Then I drilled through the already existing holes in the floor stiffeners. These are #19 holes for 8R8 screws.
Then you have 2 holes in the aluminum angle at the exact location.
Now you can screw the angle through the holes in the nutplates on the center cabin cover. Then angle will serve as a template later on to copy the location of the holes on the floor stiffeners.
Clamped the cover against the angle at the location where the 2 new #19 holes have to come for the fuel pump attach brackets.
Deburred it and then repositioned the angle against the floor stiffeners. Now you have the location of the two holes and you can matchdrill the floor stiffener using the stock angle as drill guide.
Take it appart, eh voila... there are the holes for the brackets.
Did the same on the other side and installed it using the brackets underneath. As you can see, it fits nicely.
As I had some time left, I took out 2 adel clamps and secured the rudder cable plastic bushing at the rear of the fuselage where the rudder cable penetrates the side skin.
