The ridge I am calling the south ridge is the one the Ski Hut Trail finishes on. It is not the ridge followed by the Mt. Baldy Trail, but is the long ridge immediately up and west of San Antonio Falls. It has also been evocatively called "No Name Ridge" on this forum.
From Manker Flat, I descended about 100 yards, turned right on the residential road, made a quick left on another road, and followed it to the lip of the canyon. I then slid my way down steep, hard dirt to the stream bed. After pausing for a few moments to contemplate the unappealing ascent options, I chose a steep, scree-covered slope. I then groveled up the line of least resistance (which turned out to be a lot of resistance) for a few hundred vertical feet to the ridge. The first few hundred feet on the ridge consisted of steep scree, forest, and pine needles. After that, the ridge becomes narrow, rocky, and enjoyable. This lengthy section of the ridge has a wild, untraveled feel, with lots of open rock and the occasional scramble. I followed the ridge for about 2500 vertical feet, at which point the Ski Hut Trail is intersected and solitude abruptly ends. The total elevation gain is about 4200 feet, and the ascent took me 3.5 hours. I give it a class 2 rating.
From the summit, I headed down the Devil's Backbone Trail toward Register Ridge. I've descended Register Ridge twice, and each time I made the same mistake: I left the trail too early and wound up traversing steep, loose, and generally unpleasant (even in retrospect) terrain. I had to traverse a surprisingly long way before finally intersecting Register Ridge. I couldn't believe how far over it actually was. Descending from the summit via Register Ridge took about 2:15 hours. For comparison, it recently took me 1:15 hours to descend the Ski Hut Trail.
Sorry, no pictures.