And don't forget that knots, biners, splices, and the like can reduce line strength by 50%.
Figuring the physics of effective forces and effective strengths on every angle and every part of a rigging system can not be determined without some brain power and study. Thus the rule of thumb where human safety is involved, of 10-to-1. Or if using Amsteel whoopie slings, 5-to-1 (because Samson Amsteel ratings already take into account the splices.
Rain Man
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