Thank you for the tips on the 36" radius. That's good to know. Eventually, I'll be wanting that RR Berk way down the line - if one ever comes available - which I'm sure I will need that radius to operate. To start, I'll track down a Northern (or 2).
I had the opportunity to "babysit" some River Raisin Berkshires for a time. An NKP Berk from 2001 and the more recent Santa Fe and Illinois Central Berks.
The NKP Berk would make it all the way around my 33"R curves, although there was a small kink by the Cherryvale depot that it would bump on. The more recent Santa Fe and IC Berks would derail at the kink, however. They did manage the outside mainline curve at Iola behind the turntable OK.
My AM Northerns were unphased the kink. My River Raisin SP MT-4 (4-8-2) didn't like the 33"R, period.