: Has anyone heard of a material or material brand called Sun Brella?

As mentioned it's an acrylic canvas, a twill I think. Don't now why it wouldn't due for covering except it isn't cheap and its main characteristics are UV resistance and freedom from rot. You'd be paying for the UV protection and then having to cover it with your water proofing. This stuff is incredible, left in the sun it lasts for years. Usually the dacron stitching degrades and has to be redone every few years, but the Sunbrella just keeps on truckin'. Defender.com has the best prices I've seen.