Locomotives 19 and 20 operated on 24 deg. curves on both the Sumpter Valley and the White Pass. Since the 19 was converted to oil firing though, the fire pan interferes with the rear truck and I don't know if it can still take that sharp of a turn. The 20's fire pan was constructed differently and does not have that problem.
I heard something about a proposed alternate loop at Sumpter, and if this is in reference to that we already looked at it and it won't work. There is not enough room without crossing Cracker Creek twice.