Excuse me for butting in here, just a couple of points about your discussion, that have probably already been put to bed, but anyway....
Surely if a rotor system was at working speed in a vaccum, movement of the disc would be impossible, therefore gyroscopic properties are not present. As opposed to a gyroscope which is fully functional in a vaccum. The fact that phase lag is taught as always being 90 degrees appears to be inaccurate from other posts, for a system to show gyroscopic properties surely the angle must be exactly 90 degrees always.
I'm sure you guys will tear my long thought out theory with zest.