David: While I don't run on Fastrack, I'll give you my general experience with three rail derailments.
My opinion is the middle rail is not an impediment to an engine or car careening off the rails if enough momentum is available or there are multiple cars involved. I had my boyhood 2343 Santa Fe F3 take a header off my boyhood table onto a concrete basement floor that left a crack up the nose from the anti-climber to the headlight; and that engine had "good" MagneTraction from the factory and was running on Lionel tubular track at that time.
My advice plan for any eventuality while pondering your levels of risk you're willing to take on a derailment. The weight of Gauge trains does help stay on the rails, but excess speeds due to too-tall gearing always lurks in the background.
