There is another consideration that has not been brought up regarding radii and couplers. The 72-foot shortened versions, similar to AM Budd cars, with American Flyer compatible couplers should pose no problems. The full-length 85-foot versions will not work with R20 curves. However, they will better negotiate wider but still narrow curves if there is an option to have scale, Talgo-style couplers rather than body mounted couplers. I have American Models' full-length streamlined and heavy-weight models with AM scale-sized couplers and high-rail wheels that will work on even 25-inch curves--if operated slowly--every curve except one "industrial switcher only" curve. In an attempt for more realism, I tried body mounted couplers; but they caused frequent derailments for the full-length passenger cars.
I would suggest an option for Talgo-style coupler for those who need to compromise between prototypical realism and realistic space limitations. For those who have the room, body-mounted couplers would be their first choice for the greatest accuracy.
