I agree with bearpaw. I have used a poncho tarp a lot of times - with a minimalist bivy. It works, but there is some sacrifice. If you just want to plop down and sleep under a shelter it will work. If you want a litttle more space for gear and moving around then the 8x10 might be a better fit. It would be cool if you could eventually get both size tarps that you are considering, for versatility. My kit is not always as light as it could be - but sometimes a little weight is worth the comfort - to me.

Thats wild about that poster attacking you like that - never seen that before.