Before I attach the bottom skin, I wanted to create a platform for my COM1 and COM2 antenna. I chose Comant CI-122 which are belly mounted antenna. I followed Tim's footsteps and put them aft just under the seats... good location. I used 1/16" 2024T3 clad plate and 1/16 6061 3/4 x 3/4 angle. The angle is on one side where the rib flange is pointed the other way. On the side with the rib flange, I will just fasten it through the skin. I had to form the short flange because it was about 75° and could not use angle. I cut three radius on the back side flange so that I can buck the rivets that secure the floor pan on the other side. Once I have COM 2 plate done, I will alumiprep and alodine the parts.