I haven't used it on any projects, but years ago (long before sil-nylon) all tents were made with cotton canvas. About 1970-75, nylon taffeta became the material of choice for obvious reasons. Most cabin tents and wind-proof clothing were made with taffeta nylon. Floors were often the heavy material still used in family tents today and roofs were still made with canvas
, but the steep side walls were uncoated taffeta nylon.
Then came the dome tents. I still have a huge dome tent - one of the first to come out - that is completely uncoated nylon taffeta. (Burn, remember the huge orange tent I used in Serenity Hollow all the time?) I have stayed in that tent with half-a-dozen kids in pounding rain and stayed dry several times. I had that many kids in my tent because other tents were not faring as well. The tent survived a small tornado with ping-pong ball size hail in Jones Cove, TN. I was in the camp store watching - It laid the tent flat for several minutes, but the tent was fine afterward - and amazingly it was not really wet inside. I did use a homemade waterproof footprint (cut about four inches all around smaller than the floor) with that tent because moisture from the ground would collect under my inflatable mattresses if I didn't. The tent also had to be staked though it was free-standing because it would blow over (the wind would get under the rain fly and pull it upward like a kite).
If you experience any problem with leaking with your tarp (except in the seams which need to be carefully sealed), I'd suggest pitching it so the sides are steeper.
I'm using nylon taffeta to cover the top portion of the pad cover in the sleep system I'm making now (the pad cover is similar to Big Agnes's design except it is a double with a 6" wide insulated area between the two pads and has stuffable fleece pillow pockets built in so we don't have to chase our pillows all night
). Taffeta was used extensively in sleeping bags before ripstop nylon came into favor. I still have a oversided car camping bag purchased in 1973 that has been used in the neighborhood of 1,000 to 1,200 nights. It has two small rips. This stuff is very durable - more durable than ripstop nylon IMO. However, if a tear starts, there is nothing to stop it from enlarging as there is in ripstop. I patched a small tear with an air mattress repair patch about 20 years ago - the patch worked for another 6 years of heavy use.