Can I make a suggestion? I would make 4 4" panels and treat the first and second reflection points. Then I would use the rest to make corner traps 1'x4' and straddle the corners up front.

When I was treating my room I went slow and found in my situation that first and second reflections were more than enough. Treating the rear wall sucked too much energy out of the music I was testing with and made everything sound flat.

You are finally doing it! You will be happy I am sure. Detail, focus and localization of sounds are the biggest improvements we have enjoyed. I'm excited for you. smile