Hmmm. I saw a guy try 4 fingers in a dovetail saw once. That poor little saw didn't know what hit it.
I have written about this before so I won't go into detail. But people today are taller, heavier, etc. on average than they were in the 18th century etc. Along with that, of course, is the increase in finger length, girth, etc. So naturally the average saw totes would seem smaller from days gone by. This is not to say there were not exceptions to the rule back then or now. As we grow older our hands and fingers tend to increase in thickness as well along with our waist line. . I was once considered average height at 5'9". Now that is considered short. So I make at least 7 different size handles. I am guessing Issac, and Mark do as well. This is something a production maker of anything would have a difficult time doing while maintaining the proper percentages of the various sizes of handles, saws etc. So they go with the most average size. So how many custom size chisel handles do we see out there. Hmmmmm. Zero. It never hurts to ask a tool maker if they can make a custom template for you. CAD can be a wonderful thing. Try Mark or Issac if you like their saws. You never know until you ask. I have altered mine a time or two for someone. It's just a courtesy. Not every thing can be about money.
Well there goes my monthly quota for rambling too much. I'll shut up now and go away. Best wishes.