Some time back I posted some flight test results on the dual ventral fin installed on my ES. The yaw stability was increased by about 30%. Is that "worthwhile?" I don't know and I haven't flown much with it on, so I don't have an opinion so far. Since the tail is the same on all 4-place Lancairs I think one can assume the difference is the same for all. The relative desirability may differ. I am a little skeptical of the improvement to be gained by the leading edge "extender" as it increases the sweep angle of the airfoil, which generally reduces the lift for a given angle of attack. The ventral fins also have a high angle of attack, but they are essentially blades of zero thickness, which increases the lift at small angles of attack.