I made this a thread of its own because this new video will likely get overlooked in my lanyard thread that has been around for a while. In this video, I compare the impact to a gallon jug of water of two monkeys fist lanyards, on contains a 1" steel ball and the other a 1.5" ball. I would imagine the impacts would be similar from a similar size rock from a sling as the techniques are similar and the speed generated would also be similar.

‪Paracordist's: Texas Saints ...;rlm; - YouTube