I don't know that there is a hard and fast rule. Guidelines may
differ between clubs and/or club organizations. All of the burgees
flown by our club members are the same size, regardless of boat size.

That's pretty unusual.

The same burgee that looks "just right" on a 24-footer looks like a piece of
litter acidentally snagged on a burgee staff when displayed on 65 or 70-footer.

Are all your boats similar in size, without being identical? Maybe a Boston
Whaler owners club, or some such?