I parked about 0.5 miles east of where the dirt road I would start out on intersects Upper Big Tujunga Cyn. Rd. (just west of Alder Creek). This is the closest place to park given that most stretches of this road are marked "No Parking". Walk up the dirt road for about 1.3 miles to where it crosses the main ridge at a saddle. Then turn on to the ridge for the remainder of the route. I returned the same way, but there is/might be a trail that you can take down from just north of Round Top to Loomis Ranch where you could then return to your car via the Alder Creek Trail - which may or may not exist. Some maps show these trails.
Do not count on any shade unless you want to crawl under a manzanita. It was a cloudless day, a windless day and I forgot to put the 40 oz. of gatorade in my pack (which stayed chilled in my car). Suffice it to say I ran out of water with about 2 miles to go, and ran out of energy (usually provided by gatorade) with about 0.3 miles left. I sat down on the side of the road in the shade to cool off and gather some energy when a couple of bicyclists stopped and offered me a few ounces of water and made sure I was gonna make it - thanks guys! I think it was more of an energy thing and overheating due to the lack of shade more than a lack of water (I overheat very easily). Lesson learned - don't forget your energy source.
A casing (7mm) - saw lots of dead bottles on the lower parts of the ridge...


View of the ridge and the summit...

A size twelve widow maker (on the right


Ze was here...

Brought these loppers along just in case I got myself into some brush that needed a trim (they weigh less than a pound I think)...

More pics.
Google views of route...

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Click to see full size image