I'm fairly new at this, and I experienced the same issue. From what I've seen, the hang calculators out there are reasonably accurate for a starting point, but there is no way they can factor in the stretch of your specific hammock material or suspension. At 270 lbs, my HG single layer 1.6 stretches a lot. I just upgraded to a heavy double layer WB Blackbird, at this weight the few extra ounces justify the switch for structural stability.