Dave,
Your estimate of the ROW at the loop is very accurate. From the highway you can actually see the exact location where the ROW crosses the pavement, then loops and quickly gains elevation. The ROW is indeed above the highway between the loop and the final curve leading to Red Mtn pass, although the highway cut has eroded the the hillside and obliterated the RR grade about halfway up the hill. A few years ago there were remnants of ties in the lower section, but they have gradually disappeared. Interestingly, a short distance up-gradient from the loop are two thermal hot springs that discharge onto the ROW. Someone has tapped one of the springs with a pipe and directed the flow into an old bathtub that has been placed on the grade. Clouds of water vapor can be seen emanating from the tub in winter...a rather odd sight.
JWM