forgot to add this part:

i think the yarn denier on 20-40oz PCV fabric is at least 1300 or more...the thickness of vinyl accounts for the rest of the differences. Heavy inflatable boats are made of this stuff, should be plenty strong for a ring patch. My tarps is very good about sending out small samples.
I agree that sewing is better, if possible. Need a heavy duty sewing machine or tough hands and a sailmakers needle ;)