In my alcohol ravaged brain...remains the thought that the Bell Scas system (FAA rules) required the Dihedral Sail (or Fin) for the IMC kit. The Sperry system and the Sfena system (a real piece of fecal matter) did not require that device. The CAA in its infinite wisdom did not require the installation of the fin. Having flown all the variants...with my usual boxing glove control touch....I could not see any difference in the way the machines handled....unless you had the collective/yaw pedal interconnect that the Bell SCAS system offered. That allowed one's feet to get very idle in that collective movement was linked to the pedals thus TRE's could then keep the aircraft somewhat in trim. The interesting part came during hydraulic's off flight....when the pedals moved opposite of what you expected due to the interconnecting linkage.
