He mentions some information about the dimensions and build method in this video. It seems like it is about 11x8.
I'd be curious about the durability of the material. Some members here have had luck using Polycryo for making tarps, but it would cost a little bit more. I've very little engineering knowledge, but even with the tape along the tie out points, it still seems like force will be put on the large panels between them, which is the difficulty with tarps. This could be an issue under strong winds or heavy snow. It could still be a good way to test out tarp dimensions though.