sizing small stuff

[Brion Toss]

Hello,
This is an ancient question, as you might imagine, but as far as I know we are short on answers. The closest I can come is for whipping, for which there's a rule of thumb that the whipping be square after about 8 turns of the right size twine. And this works out well, with the twine being neither so fat that it sticks in blocks,nor so thin that it is fragile and requires too many turns (too much work and time).
For service, the twine should be relatively thicker, as service must resist abrasion. And of course, as for the whipping, too thin a twine means having to make more turns. But if it is too thick it just looks clunky. For 3/8" I usually use a #42, as I recall. Somewhere in there.
Fair leads,
Brion Toss