Originally Posted by Bert Slide
It should be quite obvious to anyone who's read the stickies that there is no definitve size for DB's although a 5/8 will probably be smaller in overall size and/or mensure than most basses labeled as 3/4.
No, there's no "definitive size", in the same sense as, say, eggs or olives are classified (fun fact: a Super Colossal olive weighs at least 1/32nd of a pound). But precisely because that's the case, I'm wondering if we might arrive at some useful criteria by consensus instead.
And the goal isn't quantifying the instrument's overall size; it's quantifying the relationship between hand size and fingerboard distances. Getting back to the OP and his eight-hour drive--he wants to know what might be comfortable to play.
[Yes, we've established that tiny music teachers can impress by peeling off licks on even large basses. That doesn't mean they select them as their personal instrument.]
One diffusing factor seems to be marketing. For instance, there's a bass a dealer is advertising in my area as a "3/4 minus" with a mensure of 40.5", yet Lemur sells a 5/8th bass with a 41.25" mensure. I'm sure their physical volumes are different, but my left hand doesn't care about that--it cares about how much it has to stretch from an Ab to a B.
Fractional sizes, vague as they are, don't really seem to be germane. Couldn't we come up with an entirely separate matrix, one that correlates fingerspan ratio to string length?