if, as I understand it, the highfill curve was reguaged a bit to accomodate the 12's turning limit you might want to consider this bit of advice.
The high fill curve at mile 53, is one of the few places that actually recieves direct sunlight in that part of the canyon all day long. I suspect that with the warmer weather you had a sun kink develope in there. To prevent such future mishaps that will enevidably draw down your already less than normal revenue, I would strongly recommend the application of Gauge bars in there to hold your guage true to design requirements until your rails adapt to the warmer weather.
I am also doing this for the merchants that depend on teh Loop for their livelyhood, not becasue I want to help you out. The last thign they need is to lose ridership becasue of derailings.