I metioned the UniMog axle since they are of a portal design. By the very nature of a portal axle, they typically are used in offroad applications to obtain a higher clearnce by raising the axle tubes. But i fugured you should be able to invert (flip it over), therefore allowing the portal boxes above the xle centerline which would equate to approximately a 4" drop. Just not really sure about wms measurements. Here is a picture of what I am trying to describe. It is a very interesting possibility.
