ChefTed, Here are some things to think about:
In most situations, not even limited to model trains, things will usually work if you do a little more than is required, and a little less than is allowed. If a locomotive is rated by the manufacturer for O72 curved track, then that does not necessarily mean O72 reverse curves, and -- although the locomotive may just barely negotiate an O72 turnout -- that rating may be based on the locomotive alone, and not coupled to a long car with a coupler that tries to drag the rear of the locomotive to the outside of the curve.
