Lower???  I always thought it was a bit low to start.....  

But,  to answer your question,  you should be able to lower it to the point that the rear fender rubs (not that you want to or should).  The oil pump pickup (the important thing) is low in the bowels of the engine case.  

Note to all: Oil pump it the thing in the center of the case (3 screws holding it on) and you can see the neutral light switch to the right of the oil pump Dark thing with a brass electrical thingy.