Consideration must be given to the mass of the load and the angle between the legs. As the angle increases, the working load limit decreases.
Looking at the 'custom' © Spectra line set up on the left, you can see the huge additional load created by the shallow 20degree angle on the slings in addition to the un-tested pad eyes retrofitted onto the bow. With a dry weight of just under 800lbs the load will be around 1000lbs or above on each leg.
Which means the strain is being moved over onto the pad eyes.
Sling angles have a direct and often dramatic affect on the rated capacity of a sling. This angle is measured between a horizontal line and the sling leg or body, and applies to a multi-legged sling. Anytime pull is exerted at an angle on a leg, the tension or stress on each leg is increased.
To illustrate, each sling leg in a vertical basket hitch absorbs 500lbs of stress from a 1000lb load. The same load, when lifted in a 60 degree basket hitch, exerts 577lbs of tension on each leg.
It is critical therefore, that rated capacities be reduced to account for the sling angles. Angles less than 45 degrees are not recommended and those below 30 degrees should be avoided.
Use the formula and chart adjacent to calculate the reduction in rated capacities caused by the angle of your slings.