Nice job onthe tarp.
I have the same camo pattrn that I got at WM also, just that the suff I bought I thought was Sil turned out to be a PU coating on it. It is waterproof. How I detertermined it was PU... I sprayed a test piece of the material with sil spray and the sil spray beaded up and and wouldn't adhear to the material at all. Not sure waht it weighs yet. But thiskind of find at My WM is rare. I ended up buying the 2 bolts they had just for the sake of it.
Once I'm done with the current tarp i'm working on I'll make one with the WM stuff and see how it works.