Just an FYI for anyone that cares about grammar, I said less than 2/3 the coverage, not 2/3 less coverage. Not sure where you got 56.25 percent, but that IS less than 2/3 coverage. Back to the math, if a 10x10 provides 100sq ft coverage, and an 8x8 provides 64sq ft, then obviously the Sierra II has 64% coverage of a 10x10 canopy. I'm just talking about about the area that will be protected from the sun, assuming it is directly overhead.