That sounds like a doable experiment, but if I do that wont it just pull the door up more, I have about 3 inches of rail left before the door hits the bolt at the end of the track, it use to bottom out at the bolt on top till I adjusted the travel limit, didn't like the door hitting the bolt before it stop, so should I put a clamp behind the door on top so it wont move, then with vise grips turn the shaft?Lift your door up all the way, then put a pair of vise grips on the pipe and turn it to loosen the cables, your door will go down.
Aaron Z