Since the lower rotor blade holder is mounted (set screwed) to the outer shaft, pushing on that
little piece sticking out of it (drive shaft of the lower rotor head) might cause...

[ul] [*] Seperated swash plates. (I have even read it can seperate the aluminum ones).[*] Servo gear and servo parts to be stressed or broken.[*] Stripped servo horns, and or pushrod damage.
[/ul]

And probably other things I havn't considered yet. In the the manual (exploded view last page) it shows it
long slot down. So long slot through the drive shaft.
The long slot is so the swash linkage will have full movement from the servos to the blades.


Maybe they made them that way so you COULD put them on wrong.
But who knows why the extra slot is there.