DIY acoustic panel questions

1) For 2" panels, is it better to use OC703 or 705? Is there any negative to going with 705? Is there something even better? And where's a good place to buy them?

2) For the backer board, is that only for rigidity? If I use 1/8" birch ply or 1/8" MDF, for example, is that okay? Is there a reason to use thicker backer board? Should I lightly glue it, or just use the fabric to friction-hold it to the backer?

3) For 4" panels, is that just 2x OC703/705's, or is there some other kind I should be using?

4) If I want to do corner traps using triangles, can I just cut OC 703/705 in little triangles (2'x2') and stack them, or should I use some other material?

5) Where's a good place to buy the acoustic transparent fabric?

Thanks!
-Mark

Thanks! A couple more quick questions:

1) Is it okay to cut holes for things like light switches and outlets, or would I be better positioning them to avoid this and/or hiding the outlets? I have one case where the light switch is in the middle of where the panel should go.

2) Any preference on Mineral wool and rock-board 60 versus 703/705? They seem a lot cheaper, and according to this link are virtually the same:
http://www.atsacoustics.com/page--Se...erial--ac.html
Material pictures:
http://www.atsacoustics.com/cat--Fib...ards--106.html

3) For corner bass-traps, if I do 45-degree panels, should they be 4" think or 2" thick, or does it matter?

4) Do people generally put something on the ceiling, at least for the center channel, or is that really pointless?

That's it! Thanks!
-Mark