AH! But using the crook method only measures the length of the forearm, which can vary considerably. It has absolutely nothing to do with proper LOP.
LOP depends on a lot of different measurements, including how big your chest is, arm length, amount of flesh on your jowls, hand size, shoulder development, length of your schnoz etc.
I have seen the forearm method used and more often it doesn't work, particularly with women.
Check out the writings of Brister, McIntosh, Hill, Zutz, Churchill et al. They all agree the crook method is useless. (Of course, they would all agree my opinion is useless also!)
I am more interested to see how Gizmo's system works. Sounds like the "Try Guns" some fitters use. They have built in measurements and the stocks can be adjusted in several planes. Once they have the right measurements for that particular type of gun they can be transferred to other guns.
Most fitters use a try gun of the same type you will shoot, eg SXS or O/U. Apparently measurements can vary for each individual for different types of guns.
Come to think of it, I have never seen a "TRY" gun for Autoloaders. Did see one for pumps once.
When I use the Forearm crock method I have to bend my wrist to reach the trigger. But then I am no threat to Dan Bonillas or Gabby Hulgan either.