[g3rain1]

What glue is safe for the styrofoam diffuses? I want to stick them to a wood backing.

[S Clark]

Elmer's white glue. 

[Mariusz Uszynski]

I glued my Vicoustic Multifuser DC2 styrofoam panels to the ceiling, using "LePage PL Premium Fast Grab Polyurethane Construction Adhesive.

[corndog71]

Maybe Velcro command strips.

[Mariusz Uszynski]

Maybe Velcro command strips.

Velcro is really good idea too.I used industrial velcro for my Cinema Round Premium panels on ceiling and walls.

[timind]

Maybe Velcro command strips.

I used the command strips to hang a couple diffusers on the wall. I had to use 4 strips for secure hold.

[mick wolfe]

I've successfully used both LePage PL300 and most recently Aleene's Original Tacky Glue. 

[kuroda99]

Besides glueing
How is everyone painting their foam diffusers

[PumaCat]

I also use 3M Command Strips for the 13-root styrofoam quadratic diffuser panels I have mounted on my ceiling above the listening position. I use six strips per panel, and have four panels, in alternating orientations, mounted.