Today, I made a stiffener from a piece of the firewall channel I had left over. I drilled two rows of holes 1 1/4" apart through the roof, and then attached two pieces of 3/4" angle on each end to tie it to the bulkhead. The flap cable comes down through the slot in the forward part of the channel, and goes through a cable guide where there is a slight change in the angle. The stiffener is to reduce any flexing of the roof where the angle change occurs.
