So I've been looking for a place to mount a CB Antenna. I didn't want to use a magnet base and I don't have easy access to the rails since I have the BakFlip cover on the truck. I also didn't want to drill into the truck. So here's what I came up with. I found a thin bracket that was pretty strong. I loosened the black metal cover at the back of the tailgate and slipped the bracket behind it. I drilled a hole where one of the stock screws was located. It holds pretty firm with one bolt. When I'm not using it, I can just remove the one bolt and take the bracket out. It doesn't interfere with the tailgate or the cover and doesn't block any lights. The bolts are in finger tight right now. I just wanted to mock it up. I'll get some shorter ones to replace the ones on there now.
Sorry for the graininess of the pictures. It was dark out and I used the cell camera: