Did some more work on it today:
I needed a piece to mount my electrical boxes to so I made this piece. I also think it gives it a nice look.
Center the electrical box in the center of the horizontal piece and trace with a pencil.
Drill a hole big enough to allow the blade of the jigsaw to fit.
Cut.
I drilled and screwed 2 1/4 inch screws on both sides and also used a right angle drill to screw up through the vertical piece into the top to close off any gaps.
And there you have it, everything is done except for the electrical stuff. I'm going to wait to put the back on as it will be easier to have access to the back to staple down all the wiring. I have two boxes because I want to be able to set up two rheostats, one for the bottom two rows and one for the top two, since cold air falls and will likely need to be set at a higher temp than the top two.