[Puzzdre]

I would add that row of holes north and south of the center, like in your first drawing. Than, open the squared area in the center (4 x 4 holes, designated with yellow square in bb2k's pic) for ALL directions, like the original #Rotor design is, and then try to open more outer channels for less restriction and water drainage. You can also try to do the center square with smaller drill bit and one or two more rows of holes in same area, get the thicker pattern with more posts and still lots of turbulance, than go with larger drill bit and open toward the outlets...