There's no prohibition about plugmold facing downward.
Why not just mount it to the bottom of the cabinets and call it a day?
The only way that the plugmold would be visible would be if you were laying on top of the counter.
I realize this is an old post, but wanted to comment on a customer I had who had tile on the wall over the backsplash and did not want anything visible on it (such as those ugly things called receptacles). He wanted the prewired, rec. every 6", plugmold on the bottom of the cabinet facing down.
Rough-in was carefully planned so Romex tails could exit from the wall precisely at the cabinet line so it could be sleeved in 3/8 flex carefully clipped tight to the cab. bottom and enter an entrance fitting for each of
the two runs (one on each side of the sink.
GFCI breakers were used. The installation was kinda a b1tch, but the precious tile was unblemished by those pesky "convenience" receptacles...which brings be to my point. There was nothing convenient about bending over and craning your neck to plug things in. Of course, certain things just stay plugged in, but for my money I want a straight on target for the plug in my hand so I don't have to become the "India rubber man" contorting my 66 yr. old body to plug in the popcorn maker.
Some things just need to be practical.