Thom, the smaller one on a diamond, if waterproof, should work fine, as long as the measurement is along the side edge. Last years measured from corner to corner, so an 8 1/2' would be too short, IMO. The one I have is an actual 12x12, along the edge, so the ridge is 12, if you tried using this on a diamond, you would need a lot of room between trees......RR