Jake, I worked on the system and I am pretty sure that I have figurated it out

The diagram showed in the Murray's does wourk out at 8:1. However, it is possible to re-arrange it to 16:1 but you will not be able to ajust it from both sides.


Another point, on my 8:1 system, you might argue that if two peoples pull with a 10lbs force, the total pull would be 20lbs. However, the rope tension is 10lbs and if one of the two person would pull with less than 10lbs, let's say 9lbs for example, he would not be able to hold the rope.
If the other sides is anchored by a cleat and something else, the anchor is actually pulling on the rope with an equal force