Wow - this is a really Great Question.
For starters, I have relatively large hands & long fingers, so this is not an issue for me:
I have 2 bikes w/ Galli (one in final build), one with Universal & one Modolo.
I went out and tried to take measurements to answer the question, but found that shape of bar, placement of the brake lever on the bar, rotation position of bar, kinda made the numbers meaningless. And with original hoods, repop hoods and no hoods = measuring the dimensions of the actual metal bits wasn't accurate enough. (sorry, not disassembling bikes for measurements, hahaha)

My only experience with a Ballila brake lever hood - a relatively intact, transparent set - was that it was long enough, but slightly too small to slide onto the 'body' of a Universal or Galli.

for my Galli brake levers i'm at the decision point of altering a cheap set of some new hoods, or continuing the search for an original in 'nearly new' or a reproduced replacement.