Well, it took me long enough to get around to it. The top is now glued together and the block is finished. I just need to cut an O-Ring for it and then somebody can test it.
I decided to forego the interchangable nozzle plate. It's an option that will be included in the plans but I didn't see a real need to include it in the prototype.
And there you have it. The $8 whitewater clone.