This is where the design stands at present. The fins are 0.25" high and the nozzle array is going to be an optional insert (I have to redo the drill pattern).
Would there be any real performance advantage to having multiple outlet barbs (2 or 4)? The center inlet at present is 1/2" NPT to allow for a much higher ID tubing (or smaller if that's what you want for some weird reason) and the outlet is 1/4" NPT.