imabell said, "way way back in another time rotor blades were made symmetrical for the sole reason of limiting...."
Not true, the old days used aluminum spars, and making an assymetrical airfoil was too hard, so symmetry was imposed by manufacturing.
Modern blade spar materials and modern adhesives allow us the shape them the way we want (and twist them oddly, too.) That is why we have those airfoil sections and tip shapes.
The myth that somehow the pressure distribution and moment wander on a modern airfoil will not die will it?
OK, does anyone out there have some real data to show the "center of pressure changes" that are now part of pprune legend?