Thanks John, I may give them a shot.
alb, I was thinking the same thing - theoretically a recessed one way flap valve at the top of the scupper may work OK, although it may drain way too slow, and it would inevitably let some water back in. I might try something like this before I take 3 months off of work to try to build the vortex gadgets.
How could Potter get everything else right but these damn scuppers?!