necrails posted:Do you think that S curve in the upper return loop will be an issue?
HERE? 
For O42 and smaller equipment, no, I don't see a problem going from O48 to O72 LH turnout. -Ken
One could substitute an O60 for the O72 turnout, and put a 1-3/8" section between the O48 curves and the turnout, but I don't see that as an improvement. Trade-off a tighter turnout diameter for the 1-3/8" spacing - no clear effect on what the train experiences. My intuition is the O72 wider curvature is the better, but I cannot prove this, nor have I run any experiments to verify.
It will work to swap the O48H&Q with an O60 curve, and swap the O72 turnout with O60LH turnout, with no spacing between. Not sure if that would be better either, but maybe. The siding lengths would become 1-3/8" shorter. These are the shortest passing sidings in the plan, and I was interested in maximizing the train length that can fit.
Certainly reverse "S" curves are to be avoided, but can be acceptable if the curve radius is substantially wider than the equipment specs. For the above, O42 running through an O60 "S" (of 22.5 degrees in each direction).
There is a solution that fits, with a 1-3/8" fitter between the O60 curve and O60 turnout, but requires that the two turnouts at the right end of the siding meet WITHOUT a fitter section - meaning that the roadbed has to be trimmed on the O60 turnout. Might be worthwhile.
