We're interested, but it's looking like you're about to hit a wall, and share the experience, so we all wait in anticipation.
You've got a flow balancing problem:
1) you'll find that there's more flow through the fins closest to the outlet (how much, dunno, probably not significant)
2) your nozzle plate doesn't help getting more flow in the central channel, the deepest, even though each channels exit is the same size.
You haven't addressed the heat distribution issue. This design might work just fine, assuming that the central channel's extra heat can be picked up by the surrounding channels; it's hard to tell.