Jordan, that's a really nice looking tarp / tent.
I have to warn you though, I started sewing on silnylon, and only later sewed 70d pu coated, and I was stunned at how easy the 70d is to sew compared to the sil. By the way, there's also a huge difference between different sils, there's one that is sold as 1.4 oz / yd which is actually 1.6 oz yd, has a slight pu coating on one side, it's very easy to sew compared to the true 1.4 stuff. Haven't gotten thruhiker shield yet to compare.
One issue I noted is that when sewing at faster needle speeds, silnylon starts to slip more and more, at least on my machine it did. The longer the stitch, the worse this problem got. This problem was so bad for me that I went from a 1/8" stitch length to about a 1/32 at worst on the same seam, and it was very difficult to control it. Controlling it also is an issue in terms of the bottom layer deciding that it is really going to go elsewhere than you intend, even with pins.
So sacrifice a few 5 foot or so lengths of silnylon, get some cheap seconds, and try sewing a few large panels together and see how the stitch lengths go on your specific machine, at different speeds, and how easy it is to control them as you go down the seam. The slower the needle speed, the easier it is to control the stitch length. Just cut the seam out each time for each test until you have a good feel for it, you'll not regret spending that time. Shorter seams will not show you some of the problems, like when the fabric weight of larger pieces starts to pull on the seam and wander around.
If you think hemming the 70d was tricky, wait til you try the sil. Ironing at reasonably low temps will sort of crease the sil, but not as nicely as the 70d.
I'd get a 2 yards of cheap sil, and then take your two biggest panels and try doing a real seam all the way down them to see how the material handles, that might save you a lot of grief on your final tent/tarp.
I wish I had the room to sew a tent, but I don't, will have to settle for just getting inspired by the cool stuff I see people do here for now, oh well.