Something that I don't understand about that 4-plex...it appears to have been designed so that no matter how you mount it, you always have a phase conductor on the top. It could as easily be built so that the phase conductors were on the inside
Personally, I believe that if 'ground up or down' has _signficant_ merit one way or the other, then the solution is to go to plugs where the base of the blades are insulated.
-Jon