I discovered a corrugated polycarbonate roofing material that claims to 'completely' 100% diffuse sunlight. Palram/Suntuf Dynaglas 'Solar Shade 25'. Also non-dripping.
Corrugated Greenhouse Panel With Condensation Control | Palram Americas
Here's an article about growing with diffused light.
Diffuse Light for Better Plants
Do you have any experience with this stuff?
I haven't received my order yet, but I'm interested if others are using this. Local flower growers seem to be using it, but the marketing materials and sales support are pretty sketchy.