Just about finished the outer loop. I ran two tests to check clearances by rolling some of the longer/larger rolling stock over the track and found...discrepancies. One I can live with - a rough join between track sections. But the other...the cars goes into a curve and just...stop. Worse, this is the curve in the very back of the layout.
This one will take some detective work. The leading theory is there is just a lot of friction being generated in the turn. But its supposedly a gentler turn than the middle loop and its on a grade. But friction overcomes gravity.
I'll be playing around with it some more. My worry is that as a train goes through the curve the additional drag could cause uncoupling or derailments.