What I've gathered so far on the truncated Kamm tail section is, is that the amount of aerodynamic slipperiness gained by tapering out the rear of a vehicle to an aircraft style point or edge makes the vehicle less practical to use on the ground except in a smooth straight line with no wind changes. In a passenger car, storage capacity, ease of access and parking far out weigh a few miles per gallon. What Kamm found was that you don't need to make a long tapered surface to effectively recombine the air as it travels around an automobile. All it takes is that the rear of the vehicle needs to narrow the back end enough to get the recombination flow started smoothly.
Having read an Internet article on Kamm's findings and knowing some basic aerodynamics, this is how I would apply the information towards my safety on a motorcycle zipping around at very high speeds.
Adding a longer tapered tail section in most cases will smooth out the air flow in a straight line.
The safest and quickest way to find your optimum shape and size is to have free access to a 250mph wind tunnel.
Even after designing a perfect slippery tail section in a wind tunnel there's no guarantee Mother Nature is going to let me use it.
The farther the tail extends past the rear axle, the more leverage it will have to move the bike around during bad turbulence or cross winds.
In the air, a plane with a big tail section in bad turbulence or cross winds will pitch and yaw but its not that big a deal since you have 3 axis of control.
Momentary pitch and yaw on a motorcycle at speed is a very bad thing.
That being said. It would seem that the small performance gain from using a long tail section is out weighed by the risk of "loss of control" on a motorcycle at speed.
Am I on the right path here?