In Reply To:
If you need to noticably shorten your stroke to accelerate, you're not doing it right. Instead, it should be a matter of increasing power applied/stroke rate rather than decreasing stroke length.
Maybe theoretically.
Maybe. But in practice, that's what happens. Think about your water polo games--when you change direction all of sudden, aren't your first few strokes short and choppy as you get up to speed, and then they lengthen and smooth out? Mine are (or more truthfully, were; haven't played water polo in a long time).
I think the bottom line with flip turns is that a mediocre swimmer can realize some significant benefits by learning flip turns though improved "water feel" and better streamlined body positioning, and keeping the strokes in long, efficient cruising mode. Then the secondary benefits of cardiovascular benefits of breath control and swimming in the fast lane. Last and probably least, the psychological factor: if you feel faster you'll be faster, just like on a new bike.