Thanks guys.
I remember reading Rustys review of the SD70 he purchased along time ago and he said R29/R30 curves was about all one would do with fixed pilots.
That was with Kadee couplers:
I have no idea what the minimum radius would be with fixed pilots and Flyer couplers, as the couplers on a following Flyer freight car doesn't move independently of the truck like a Kadee does.
The overhang of a fixed pilot on 29" radius is fairly severe:
Rusty