It has been many years (25+) since I last drove the Abbott Road 4610. I started at High Rock and traveled west, and I recall at least one tricky washed-out area. What is the current status between Twin Springs and High Rock?
Plaza Creek trail goes about a mile or so from Twin Springs then seems to get swallowed up by the loose terrain...
My daughter and I spent a lot of time last summer clearing brush on that trail, but we had my little one with us so we only made it about a mile. I think it gets really faint the lower you get. Don't think that was a major route, especially after the Abbot Road was constructed in the 20s.