Thank you, Bryant.
I was thinking much the same - 6 posts.
Here's the pergola I had in mind:
I'd be using 9'x6"x6" posts for mine. The pergola in this photo is, of course, using just four 10'x4"x4" posts. Otherwise, mine would be much the same. 2"x6" beams (I hope I'm using that term correctly) across the long side of the structure, two of those on each side. I'd then use 13'x2"x6" rafters, probably spaced out every foot and a half or so. And then again across the long end on top I'd use 17'x2"x4" wood, just like they're using in that photo.
I'd definitely want to add the knee braces, like on this one. I think i'll be planning on notching all these timbers together, as well. I like pergola look when they are notched together (unlike this one).