Primary source on the V grade system

Its well known that John Sherman invented the V grade system for his Hueco Tanks guidebook. Does he actually explain his philosophy for the grading system in the guidebook or is it just there without any context? I don't have the guidebook or else I would just check myself. 

More generally are there other foundational documents that can be treated as primary sources for climbing grading systems? The closest examples that I can think of is the Jim Bridwell article on splitting YDS grades into lettered subgrades.

John Sherman’s Stone Crusade may have more info.  It is about bouldering history and areas. Been years since reading it, but it’s a good read either way

From 1995 guide

For some good insight into John’s creation of the V system, check out the interview done with him on The Nugget Climbing Podcast episode 108. He delves into that, and many other fun stories, in the 2 plus hours. A really good listen. You can find it on Spotify