"Doesn't Golite use a lighter silnylon (15D) for their poncho tarp?"
Yes. Posted on another thread the weight of 1.08 osy on my scale. It is listed on the GL site as 15 denier and 1200mm HH. Medium green color. Most interesting, is they claim it is vapor permeable; that is, 'breathes' to some extent. That probably means the coating is polyurethane (PU), not silicone, like the argon.
Being a 'green weenie' (colorwise), may use it for a front and rear awnings on a 'side entry' tent, with a darker and more waterproof green silnylon for the main body of the tent. How to seal? Sil sealer on silcoat material, PU sealer on PU coated material. So lap fell seams will have sil sealer on one side, PU sealer on the other. Yes, the NAPA sil sealer Permatex will also adhere to some PU coats, so might experiment with that also.
It would be a gas (no pun intended) if the WPB really worked, but doubt that the PU WPB coat would be breathable enough to reduce condensation on a tent.
The weave is the mini-ripstop seen on many of the 15D tent fabrics, almost invisible ripstop except when light shines through. Based on Roger Caffin's observations of leakage of ripstop materials, the finer ripstops should create less opportunity for leakage.
In the last couple years, 15-20D tarps, flies and tent canopies have multiplied in the market, the manufacturer's preference leaning toward PU over sil coats. Not sure why. Have been using high HH 30 denier silnylon for tent floors for several years with no leakage; so doubt the often stated view that the PU coat is more durable per se. Using a 15D 3000mm HH silnylon for a main tent, with a 15D 1200mm HH PU coated nylon for the awnings should yield interesting results in serious rainstorms.
But ordered samples of the Argon sil to check out the colors - the swatches are not large enough for a reliable weight figure. If one of the colors is light enough for me, will order a yard and test-wash-test to check the HH. With the low price, this could be a real boon to MYOGers if it can maintain waterproofing over 1500mm in ordinary use. It will be a wait and see proposition, though. Better safe than sorry.