I really want to use a 300 LED strip, these are 5m or 16.4 ft.  Then I cut this in half and end up with ~8ft 2".  The challenge with this that plywood comes in 4x8ft sheets.  So I will have an extra 2" plus 4" (need 2" space on each end) that means I need an extra 6 " more than 8ft.

I also need the cabinet to be pretty strong resist warping and sagging.  It will need to be reinforced, at the same time I don't want the box to be overly heavy.  Again the classic trade off.  It would be much easier to just do a 146 LED and fit into the 4x8ft mold.

I want to be able to slide out the LED panel from the cabinet, and also have a slot for acrylic defuser  (not sure if I will have one in phase one).  To give the cabinet strength I will use 1/4 hard board for the back, the LED and Defuser will fit into slots and slid in.  I will have a end piece that will close the open end.  I will have a small gab between the hard board and the plywood that the LEDs are mounted on, this will allow me to hide the wires.  I am going to paint the plywood that the LEDs are mounted on white.

Then I need to deal with where to put the Arduino and USB Host module and power supplies.

At this point I would like to have the Arduino and USB Host in the LED cabinet and have a separate box for the power supplies.  There is the issue of how this will look to people, it will be much cleaner if they see one 8ft 6" x 14" cabinet.  I'm very concerned about heat with the power supplies.  I will keep them in a separate box that will be mounted close by but not in the same visual path.   I am designing the layout for both of these, and selecting easy to use connectors for all the power cords.  I will run one 120v power line and split this between the two power supplies inside the power box.

I don't want the cabinet to sag in the middle, so I will have at least four mount points, maybe five.  

I am going to pay very very close attention to the LED layout, I want to make sure the LEDs line up accurately.   From my experience with the 20x15 matrix, this is not easy to do.  I am going to 3D print some mounting brackets for the LED strips.