It's really hard to guess exactly how it would have gone once you entered the shop. Again, speaking only on the matter of rapiers, "fit" was a matter of very personal preference.
Oddly enough, when you say...
It sound reasonable that a taller person may elect a longer sword than a shorter person.
I'm willing to bet that it was pretty much the opposite of what you'd guess!
The use of the rapier was and is, more than anything about REACH. A short statured swordsman would want the longest blade he could manage, to compensate for the lack of "reach" over a taller man. Remember, with a rapier, blade length is pretty easy to work around when it comes to how that blade handles and balances.
With the right combination of blade thickness, hilt style and size of pommel, rapiers could and did reach sometimes ridiculous lengths. I seem to remember hearing of blades as long as 48 inches or more.
The blades I duel with are all 38 to 42 inches, and I find 42 to be about my limit, but then I don't practice 8 hours a day as some students of the period did!
(must be nice to be the "idle riche"
So basically, I would imagine Joe Customer, or if you prefer, Guiseppe Customerri,
walked into the shop, told them what blade length he wanted, and then collaborated with the maker to determine what hilt style and pommel would suit the user's tastes and give the balance needed.
For fine tuning, the pommels were probably swapped out until the "feel" was to the customer's liking.
(Disclaimer)
The above is "educated guess" not historical fact. If anyone can confirm or deny, I'd like to know for sure myself!
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Tráceme no sin la razón, envoltura mi no sin honor
Usual Suspect