Barry,
I believe that is indeed Mr. Underwood. This stabilized gif shows no hat while his glasses and raincoat are evident. The above annotated frame was grabbed while Underwood was leaning (or is it bending?) into the conversation with Craig while Darnell cranks his camera spring. Don Cook is present in some of the TSBD doorway scenes, some including Howard Brennan. Cook was not wearing an overcoat or raincoat, iirc.
Much obliged James. I should know better by now than to use a still frame, especially when the full clip I just posted the link to... anyway, well worth it for that stable clip, ty.
Naturally we'd think that's Haygood again in the background but I guess technically it could be Hargis if it's around three minutes into it.