During a couple recent runs to joann fabrics where I skulked the red-tag fabrics I found a bolt of polyurethane coated polyester. At $6 per yard I was thrown off 'till I saw an add for the "firefly frenzy" with an additional 50% off red-tag fabric. I figured it had to be waterproof and would give me some nice DIY practice on tarps.
I decided on a 5' by 10' tarp with 10 tieouts, and for my work I think it came out pretty well. The tieouts are 1" GG-webbing reinforced with light camo polyester.
What I learned--
Having been frustrated to no end by the reinforcements on my first DIY tarp, I sought alternatives to the "pull on one piece and kind of the other, hope it comes out ok " method outlined on Blackbishop's Blackcat tarp guide (not to insult the guide--it helped a TON on my first DIY tarp).
Before I attached each reinforcement patch, I rather generously applied "Liquid Stitch" to hold the patch in place. When I took it to the machine, running lines of stitching was a cake walk without fumbling to keep each piece in line and taut against each other.
I'm just about sure you could do something similar with silnylon using a diluted silicone caulk or a seam sealer as glue.
Might be a noobie tip or have been brought up before, but maybe it'll help someone
P.S.--Has anybody used PU coated polyester for a tarp that could comment on durability/quality?..