I didn't mean the small wrinkles under/adjacent to the tape; I meant the long waves of loose material running more or less parallel to the ridgeline, the same thing you're calling tautness.
I know what you were referring to. I've not had any issue with those, but I don't pitch A-frame either so maybe that's worse. I'm thinking of playing with that this summer though (7x10 for my son and I). Looking at pics of others' plastic tarps in A-frame leads me to believe that it isn't a concern.
Thank you for all your advice on this topshot. Since I'm doing this all by the seat of my pants, your input has been invaluable.
Go ahead and push the envelope. That's how we find new discoveries. I need to snag some of that nylon sail tape David Gardner found. I wonder if that will make sewing any less gummy.