This is the view inside of the ceiling with the new wire pulled in through the hole in the laminated beam.

The two gang plastic old work electrical box is mounted to the wall by tightening the screw in the upper right corner and the screw in the lower left corner. The wings will be pulled from behind against the wall and create a tight wedge. In addition a #8 x 1″ sheet metal screw was driven through the box into the adjacent wall stud for additional bracing.

The completed installation of the Lutron Diva Dimmers
Close shot before the dimmers are mounted to the wall. All of the white neutral wires are spliced together and tucked into the back of the box first