The USFS and the BLM have done extensive tests on this subject. I dont know who is in charge of the USFS rotor wing / rappel program these days but it would be out of the NIFC in Boise ID. The tech center did tests on all the ropes, brackets and devices. A couple of years ago they did some neat drop tests on when they were designing the overhead bracket for the 407.
And courtesy of your tax dollars it is all public information.
RB