I've wondered this for a while. May as well try and stop wondering.
How important is the player's Primary Position on D? For example, if I play a SS (primary) at 3B, will he perform exactly as well as if I played him at 3B and changed his PP to 3B?
I realize that the PP impacts the auto-fill heirarchies, but I'm more interested in the practical impact of Primary and Secondary Positions, if any.