...and boy, was that a lot of work! Ain't no way I want to do that again unless I just can't find what I want from a vendor.
This took me the better part of two days. Granted, I was pretty much figuring everything out as I went, and I hadn't used a sewing machine for about 20 years.
I used 1.9-oz rip-stop nylon (on sale at Hancock Fabrics) for the tarp body and grosgrain ribbon for all the edge trim and at the seam along the spine. I used a polyester thread, which is like fishing line and is only about the width of a human hair. That was pretty difficult to work with, but it seems very strong. I chose metal D-rings because, quite honestly, I don't trust plastic ones to hold in strong wind gusts.
This tarp is 10' at the ridge, and each side is 4'-9" wide. The sides taper down to 7' at the bottom. Total weight is 19.2 oz. I still need to do the silicone DIY treatment, as well as add some side tie-outs. But the worst part is over!
The wind was blowing pretty good today (gusts as high as 41 mph), but this tarp behaved very well.
I learned a lot of lessons, and if I had it to do over again, I'd do things a bit differently. I'd make it 11' at the ridgeline, and my assembly process would be a bit more advanced. But like I said, I don't intend on doing this again any time soon if I can help it!