My own thoughts are that a VSL of between 25"-27" is really ideal if one is intending to play in the key of D a great deal. (most dulcimers play in D more than in any other key). Once you get in the longer 28-30" vsl range, you are going to start breaking strings a little more often, and the shorter you go ...say 22-24", the heavier strings you will need to put on in order to play comfortably in the key of D.
That's the reason epinettes (which often have a typical vsl of only 21" or so) are usually tuned higher for the key of G (3 steps up from the usual dulcimer D). And dulcimers longer than 28" scale length often do better when tuned to C (1 step lower than the usual D).
Beginner dulcimer players often worry that they 'need' a shorter vsl because they have small hands. What they don't take into account are two important factors: 1) They be using also their thumb while fretting ...which extends their reach way beyond what most guitar players do using only four fingers ...and 2) Because of the drone-friendly tunings of dulcimers in the first place, one frequently is making use of open strings while fretting chords. So it's not really all that common or critical to make a long stretch when chording. When it does come up that a long stretch is needed, your thumb can neatly solve the issue most of the time.
While I wouldn't necessarily recommend a 28-30" vsl dulcimer to people with smaller hands, I think that vsl's of 25-27" are great for people with any size hands, even small hands. Just my two cents.
Those irritated by grain of sand best avoid beach.
-Strumelia proverb c.1990