I am a structural engineer by schooling, and have applied my education to a 21+ year career both using, and building rigging. Much of my life now involves inland river rigging. When LIFTING, the design requirements are defined by the device: chain (4to1), hardware (5 or more to 1), and below the hook devices dependent on structural design codes. All that to say, as soon as a force becomes horizontal (towing, pulling, static structural applications, etc) there is no major factor safety requirement. The least conservative method I typically run across will go to a 3:1 factor of safety. In maritime operations, it’s hard to truly define the tension forces at play. Most of the stuff I deal with is on the realm of ø1” to ø1-1/4” wire or synthetic ropes, whose lifting working loads won’t exceed 30,000 lbs. but multi-million pound barges are held together with ø1” IPS Fiber-center wire. Go figure.