I'll preface this by saying I know next to nothing about cuben, except it was designed for sailboats.
I would be worried about developing a seam over time where the mylar coating might wear. Then again, the line we use is generally pretty slick and ideally the tarp shouldn't move once tied down over the ridgeline. Just something to think about.
"I ain't here for a long time, I'm here for a good time"
- George Strait