I have designed mine with this in mind. I like the tops of the valve covers to be clear of any clutter like oil fill caps and pcv inlets. It makes a much cleaner looking engine compartment and you can re-locate those items in the side covers and other spots that are less obvious. Granted, sometimes you just can't always move the pcv somewhere else easily, but it also removes the oil seepage from it and the filler cap where it doesn't stain and mess up the valve cover as well.
