Just for fun, I made a tarp out of jo-ann's ripstop. It's the first tarp I've made, and learned a lot. Cat cuts on all edges, grosgrain tie outs, etc. Happy with how it turned out. If I like it and use it, I'll probably make one out of pre-made silnylon next time..!
To mix the sil, I put the silicone in an empty milk gallon and then eyeballed an appropriate amount of mineral spirits and then shook it all together. The mix was viscous enough to brush on with a bristle brush. I did one side, then flipped it over and did the other, just to be sure. I then wiped the whole thing down with paper towels to absorb any excess. If anything, I erred on the side of applying too much, but I didn't want to do too little...
It's still drying/curing outside, so I don't know how heavy it is yet. It was about 9 oz before sil application.