The tarp I showed is a 9'x7'. I have it pitched high, but if you pitch it low, the coverage is pretty good. Your 10'x8' is roomier when pitched low. There's no magic with a tarp - if you've got the wind blowing right in one end you are going to have a fun night. So site selection and orientation is important. And you don't have to do your first try in a storm. Also I wouldn't think you need to seam seal that tarp - I thought they were sealed, but I've only looked at them in the catalog.