You know, that design makes a lot of sense, since the door would be mostly horizontal by the time the pulley got close to bottoming out the motor would still be able to move it.

I bet those tubes go below the foundation though and god help you if the cable breaks and you have to fish those weights out to reattach it.

Maybe there is some easily reachable latch point on top or some sort of fluid pump port that will make it easier on you?