So I reread the book and my esteem for Kidder's writing went up even more. In the parts of the book where he described Alsing's appearance and demeanor were spot on and captured essential things about Alsing without using a lot of words.
One of the things I recall is Kidder said something like, "Alsing is a tall man, but his mild demeanor and hunched posture presents a much less imposing figure." Sure enough, that is exactly the experience I had with Carl.