How come the propeller arc is behind the pilot in high wing twins (MU-2, Partnavia, Aerocommander) and in front of the pilot in low wing twins (Cessnas and Pipers).
I doubt there's any correlation. Look at a DC-3, a Convair, or a P-3 Orion.
What you will find is that the propeller arc is NOT lined up with the pilot's seat (for obvious reasons).
There is an Advisory Circular regarding "rotor burst planes", too, that could influence the position of the propeller disc, depending on whether the engine is a piston or a turbine.
Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout