As Alan says above, all LGB locos should handle R1s - because from the very early days of LGB, the firm decided that everything they produced must follow the "R1 Rule", in that it must run on their tightest radius curves. Of course, that doesn't mean that the bigger locos (or the longer rolling stock) will look very sensible on tight radii, but that's all down to aesthetics rather than functionality.
Jon.