I know of a reason but it really doesnt apply.Grandman said:its easy for the cotter pin to fall out , all so easy for a shackle to turn and put a load on the sides of it . then your trusting that cotter pin with your life . a threaded clevis is simple much stronger and safer .
Mike , i know of no reason that hook must be on the pin rather then the center of the clevis . Main point is not to pull on the sides .
For rigging where there stands a chance of the pin unscrewing because of load shift or change in the angle of the pull you want the pin on your no going anywhere no matter what side