I don't know, but it looks to me like a bookshelf would do a better job at diffusion.
You should be able to build something that will diffuse like that. ~shrug~
When I need diffusion, I usually go all out and do the serious math. RPG has some good ones, though I don't care too much for their latest products based on prime 7.. shallow too. Not good in my book. But their Diffractal is really good. OR you could build one. I have an Excel spreadsheet to calculate any diffusor you might need. Where's that link.. sry. I'll get it for you in the morning.
those are my thoughts...
Uhmm, you owe me a penny.