Zeffy,
Thanks for that. I think the FAA has lost the plot here. While they impose visibility and altitude limits on operators who choose not to train, the fact that it is impossible to safely fly a Cat C aeroplane within the established norms of flying eg aligned on final by 500ft-ish (1.7nm about) and stay within the circling area of 1.7nm seems to have completely eluded them.
Or are Americans/Terps operators allowed to just ignore the circling area limits if they satisfy those FAA-imposed limitations, in effect doing a Visual Approach?