Once I determined the layout and placement for the replacement forward seat, I needed to add the seat support angles.
The instructions have you rivet it to the sides of the fuselage trough/channel. I found that it was rather difficult to drill the holes for the rivets in the very lmited space, plus, all of the weight of the forward occupant (pilot) would be supported by just the six rivets in shear. The fuselage trough/channel is fiberglass with a hollow area behind it, so all of the pilot weight would be supported by total of about 1 1/8" (6 3/16" rivets) by 3/16" (estimated thickness of the composite) of composite area.
So, I changed it a little. As you can see in the pictures, I mounted the seat support angles to some aluminum angle, and then riveted the aluminum angle pieces to the top of the fuselage trough/channel. This spreads the pilot load across an area of about 12 square inches (6" long angle by 1" wide) and in compression instead of shear. The aluminum angles are still held by six rivets in shear, but they are now holding two aluminum pieces together and no thin composite is in shear.
