I have a copperjohn pro and I love it! Copperjohn would be my first choice. It is all aluminum and is a strong good sight. I also like the cup and the light that you can get for copperjohn's.
I used to have a TR but I sold it. They have alot problems. The pin guard is plastic and not aluminum. Another bad thing about the TR is that it hangs down more. That might hang low enough for you to not have fletching clearance. That all depends on how low your sight is though. I think when I had mine I also had problems with it moving alot. I would not get a TR.
I'm not sure if the Cobra has a round pin guard or a rectangle but whatever you do I would suggest staying with a round pin guard. That way you can see your whole guarde in you peep which is round. So my first choice is the Copperjohn. Good Luck!
