Many of the high end brass models will not handle the typical 3 rail sharper radius. the more detailed the underbody is, the less sharp a curve it will handle.
I think the GGD heavyweights which I have would handle a pretty sharp curve. they have much less detail underneath and are designed to use either 3 rail or 2 rail trucks.
Another issue is coupler swing. Typically on 2 rail cars, the couplers are mounted to the body not the truck and will not swing nearly as far on curves.
