Jeff,

   If you really want to see squirrely do a abrupt power loss (simulating a flame out at high speed) at 200 kts or more. This is where you could really get into trouble in the turbine. It comes very close to swapping ends. This has been a problem with a number of single engine turbine conversion attempts.  The big windmilling (not yet feathered) prop acts like a big forward rudder which is not needed plus it disturbs the the airflow over the vertical stab and rudder. The Lancair does not have excessive rudder authority as it is. A ventral fin really helps the turbine remain in control.

  On another point a high frequency yaw damper (it must react quickly to be of value) makes a huge difference in the handling qualities of most aircraft in turbulence, but the autopilot servo used for a yaw damper, that I test flew in a Lancair was not capable of responding fast enough to make a significant difference. A yaw damper will not reduce the requirement for right rudder on takeoff, climb or descent. What it really reduces the tendency is the tendency to have yaw excursions and dutch rolls.
   I flew a test at Edwards where a high frequency yaw damper was installed in a Twin Comanche and the difference was very noticeable. So it does work in GA aircraft.
  For example the 727 was almost impossible (it took a great deal of skill to fly it without the yaw damper) to fly with the yaw damper off if the airplane got disturbed by some effect (turbulence), with the yaw damper on it flew very nicely. There are several products out there that say or imply that they augment positive stability and they do not. One system that I test flew took up to 18 seconds to mount a response to a deviation of the aircraft. This was worse than no damper at all.

 On one more point the winglets when properly designed and installed (they are somewhat difficult to properly design and install, a lot of attention to detail is required) do improve flight efficiency (same speed for less fuel or more speed for the same fuel), but the biggest negative that I see is a small but noticeable reduction of the crosswind handling capability.

Jack Webb
BSAE