My understanding is that from big tree down to whitewater is super rugged. I’ve not been there, myself. I’ve inquired about the route myself via a guy who used to be a ranger at the Whitewater Preserve who had gone up it, not down, and he made it out to be complete insanity to descend. He advised against it strongly, and this was a guy who was a capable outdoorsman and a strong rock climber.
Where is Manat? I’ve traversed Yucaipa ridge from the jumpoff to the mill creek ranger station, and have not heard of Manat. Is it to the east of Galena? I’d be really curious to see that area. East of the Jumpoff is really wild country. “Here there be dragons.” Ha!
I hope you get some good beta, and I hope you report on what you see if you make the descent! Sounds amazing.