Great article! I have not read it all but I will.

I have been looking for an article/study on the difference in efficiency between fixed and geared drive trains. We have talked about his several times on this forum. I have never found information/study directly relating to this question.

What comes to mind for me is the Sturmey-Archer three speed fixed gear hub. The major downfall of these are the efficiency of the gears. There are many positives to them but the efficiency is lacking in all internally geared hubs.