I did one on the "do it with the spring relaxed and the door up" plan. The door isn't that heavy, you can just lift it with your hand to help the opener lift i

I did one on the "do it with the spring relaxed and the door up" plan. The door isn't that heavy, you can just lift it with your hand to help the opener lift it up, and done. But cramped!! Getting the lift cable nicely wound on the lift pulley, giving it a bit of preload (pull) and getting it attached to the bottom of the door, all with the raised door in the way, and doing both sides, let's just say my supply of swear words was severely depleted by the end. But I did get it done, and no dangerous forces were involved. Whereas I saw a professional do it in about 5 minutes flat on the "wind the spring and block it and then hook everything up with the door down" plan. But that can kill you if you do it wrong.