Hi Bradley--I assume it's the same Hugh G McColl--he had very much the bug for searching out McColls (and McCalls where they were part of the same grouping) and collected as much as he could in cycling around McColl areas of the Highlands. Sadly, he died in a car accident about the end of the war, 1946 if my memory is still working, and the society just sort of staggered along for a few years then died off. I assume the C in my family number (C29) stood for Canada and the SC in yours for South Carolina. S stood for Scotland. Thank you for the links in your message, I am following them up, and it's the first time I've seen any of those trees that Hugh G drew up so it's a thrill indeed.
I'd neglected the availability of new technology, but now plan (hope?) to PDF all the photocopies I have of the McColl Society magazines over the winter and make them available somehow.