I think 0.75oz/yrd2 DCF is much stronger then some of the thin silnylons/polys that get used. Even the 0.51oz/yrd2 DCF that zpacks uses is strong enough, you just lose a little abrasion resistance.>>1775818
The top tarp is small, 9'x4.5'. It's basically the roll width of the material, minus a little bit to seam the edges. It's great if you're only expecting light rain and know there will be some natural cover.
The one below is like 8.5'x8.5' iirc. It's more than big enough for conditions that will involve more serious wind and rain. But I don't take it to completely exposed areas. That's when I use my solomid, which is the tent in the bottom image.
Here's a bunch of pictures of my tarps.