For posterity, nothing in render options fixed this. Map size had no effect other than making the shadows crisper. Shadow bias had no effect on primary light as a disp. map (.010-2.00). Using Ray Trace as the primary, reducing bias to .010 maintained best pixellation, but was not a complete fix. I tested this with all other lights off and even with nothing but Ray Trace and Cast shadows checked. So...the theory award goes to DaveK! In killing refract, you solve this, but end up with a much less interesting effect. Also sunglasses! But I'm sure another glass option will work.