You did not mention a distance to the back wall.
Interpolation tells me you are probably going to have some reflection points generated from the back wall, even after some diffusion is installed, which might be a concern.
As Geno says, diffusion is going to be important, but you might also look at secondary reflection points from the back wall as another early part of your processes.
Steve has articles that have addressed some of this.
You might start here to help with ideas. Lots of concepts covered. There's more, too.
https://www.decware.com/paper39.htmhttps://www.decware.com/paper14.htmhttps://www.decware.com/achowto.htm