Rance,

The screen wall was 3/4" MDF which was biscuit joined every 12" and shimmed at the back to make as flat as possible the surface. I used a steel straight edge with a light shining from the opposite side to find the low spots after attaching it to the wall. Bondo was used because I could apply multiple coats per day (it will set in 5 minutes) and also its tough, real tough.

The concrete floor has hard insulation under it and is sealed to prevent moisture creep. I used a heavy underlay under the carpet for sound.

I still need to make black curtains around the screen and the auto 12v light shades, but wanted to take a break and watch some movies