Sounds like you got some 1.1oz untreated ripstop to me. i can see my hand through all the 1.1oz I own, but not the 1.9oz.
If it's untreated material I would not make a tarp out of it, even with a treatment. I would be wary of making a tarp with DWR material. A tarp is there for weather protection and you may end up regretting not using a truly waterproof fabric.