Honestly, I'd be a bit more tempted to forego the hinge, many $$$$, and use a simpler method such as a 3/16" or 1/4" "sleeve" about 1' long over the existing center tube. 6" goes over the rear tube, 6' stays open, then you can still use the same piece from the cut forward and just use a 1/2" tractor attachment pin to hold it in place. Get home, pull the pin and slide out the front piece.