Lifter was installed without checking that the door spring was tensioned. Result is that door comes down with a lot of force that the spring is supposed to absorb. The installers should definitely checked that this was working properly. I had to phone Liftmaster to get this information; they were very helpful. I would guess that Altwood hire contarctors to do the installations, but since they are not the manufacturer of the door, this is a MAJOR part of what they do and they should have much more competent installers.