So I've seen very little on this, apart from some very general discussions, mostly applying to the ratings once you get to doing the extreme overhanging routes such as those found in Wyoming or Utah.

<b>Does anyone have any knowledge into how to classify this rating system? </b>

I've been doing some dry-tooling/mixed climbing in Utah, Tahoe and the Bay Area, but I've had no idea how to classify the routes! I can definitely attest, though, that the rock rating has almost nothing to do with the difficulty of the dry-tooling. And like the YDS rating, you can have easy but pumpy holds, or very technical holds that require finesse more than strength, so what is truly 'harder' is uncertain too.

As a sub-question, I've noticed that for routes that I climbed that started out mixed and later in the season became pure dry-tooling routes (or where I kicked off a lot of loose ice, and those who followed had an easier time with a 'cleaned' route), the dry-tooling seemed harder than the mixed provided that in the mixed climbing you have a good sense of what ice will hold you, and what won't, and kicking off the ice that won't in order to get to rock holds.

<b>So, instead of a 'mixed' rating combined with the ice rating, or just the ice rating, wouldn't it be more appropriate to have a 'drytooling' rating as an upper bound on difficulty (where thin ice becomes common), with an ice rating as a lower bound rating?</b>

Its like so many other ratings, that ratings charts aren't worth anything. What you really need to do is just get onto a whole lot of mixed climbs in a variety of areas and styles and see what is "consensus" for a grade.

One difficulty with that is that I rarely see the M rating used! Or if it is, it is usually M6 and higher, which makes it difficult to get a feel for the lower levels that you're more likely to encounter on most rock routes.