Well, I have a small layout . . . . but the outer loop has generous curves, the smallest being in a tunnel at O-80. The rest are wider.
I made a train out of doubleheaded 3-rd Rail Mikados pulling 35 cars. The locos pulled well, but, at the foot of a grade, the front truck of the lead loco would lift enough to derail.
Abuse? I would say so. Really long trains demand straightaways or all 0-120 curves I can not accommodate.
Video of this 35 car train at this link.