Sheldon M

Question about sizing this harness. I'm the top end of small, and would likely be fine for most days. However, cold, nasty weather (and the additional clothing) makes me skeptical of still fitting the harness. Given harness is non-adjustable and the jump between sizes seems kind of big, I'm concerned that the medium will be too big. Sorry to goldilocks, but am curious about how much overlap you find between sizes and/or any advice you'd have for someone on the edge of a size. Thx!