This picture might also help.
We put the proper reinforcement in the wall, but used a 2x6 as a door jam that protruded 3/4" to the inside of the doorway, proud of the sheetrock. It looked great and then the door guy showed up and informed me that the whole mounting surface for the track, motor, and cable tension sensor, etc, had to be on the same plane.
I put 1x6 on top of the sheetrock along the protruding jam to level everything out. It is an old building and actually took a bit of shimming to get everything level matched and square. And then I painted it green to match the other trim.
View media item 84538Note the location of the cable tension sensor next to the motor required an extra board there to support it too. It's just inside of the top pulley in this photo.
View media item 84411Everything really does need to be mounted on a surface that sticks out the same amount from the wall, in the same plane.