Holy Cow:

WE might get out of this more or less all agreeing on a point.

My own way of thinking about it is just like longitudinal stability, just without the contribution of the wing. That leaves the vertical tail, the fuse shape, the prop effect, and the CG as the big (or not so big) factors.

AS with longtdl. stability, more yaw stability means less maneuverability. I think in the past, the vertical was sized by TLAR and was generally overkill.

What Ben says about large tail size and damping is absolutely true as well, but I just think the whole sizing has been overkill in the past.

I think there is a combination of things here, the large fuselage side area visually makes the vertical look small, because the amount of fin above the turtledeck is shorter. AND, the vertical is a bit shorter, but not as bad as it looks. People have cut back to where the stability and damping just starts to fall off for maneuverability.

I have nothing but observation and a little flying experience, but it does seem that a smaller vertical with 80% rudder area (for example) is more responsive than a larger vertical with the same rudder area ratio. The only real explanation is the larger relative influence of the fuselage side area.

Here's a plane designed for fully neutral aerobatics with a cheap wacker conversion motor by a friend of mine. THe vertical looks too small, but is the size settled on after plenty of development flying. I've flown it myself and it's really perfect with much response and very little wagging on a hammerhead downline - no more than any sport or aerobatic plane I've flown anyway: