I think you have it backwards. As long as they don't bottom out (the axils CV's) when their horizontal, you will only gain by lowering your diff.
The only reason we don't lower it any farther is that, 1 the cross member is in the way and 2 to lowered diff any farther might get it cought on stuff.
So, with the lowered diff (Anvil) you will have less angle on your axils and have longer CV life. If you were to raised your diff from the stock location then your axils might extend too far and stop travel but most likely just break.
GO FOR IT!