I have the Guide Gear 12x12, and yeah, huge is the word. Corner to corner it's ~16.5'. I set it with a diamond pitch, and use it as a group shelter...we get 4-5 under it, along with a small fire in my little Weber.
When I pitched it over my hammock, I went with an offset rl, leaving a 4' "back wall" and an 8x12 "porch". Ginormous.