Crab
You hit the nail there
All loads have a Vne, normally most flight manuals have a Vne of 80 kts with something on the hook. Have flown a bambi happily at 70 kts and it has got no where near the tail rotor. The same with it on a 50 ft line. Although I can't quite follow why the line has to be more than 50ft, but if that was the manual says then that is what you do ?
The pilot must have been going at some speed to get the bucket into his tail !