Nice, taking your concave concept one step further!
Personally, I'm not too sure how adding channels to a retro fish will work out--you may want to size down your keels... possibly sink in some fcs plugs for twinzer canards?
How deep are you planning to make your channels?
If you cant the fins too much, the channels wont work. And side fins on a fish usually have a good cant ( 8 degrees ). I would think the reason to having a good fish is to catch lots of soft waves, and being able to turn rail to rail and carve easily, and have a kinda skatey slidey feel to it. Not a down the line board, but a top to bottom board, so channels might not be useful. Just my opinion.
Can you do a step by step, like pretend you are teaching a child how to do this, like 'I am doing x because of y', etc etc. I am interested in learning about this process as I have only sanded my boards, never shaped one. And the ones I sanded were from a CNC machine where I choose the specs and rocker with the shaper. I have ridden many a board and I know what works for me, but overall the finer points are not my forte' and Id like to learn and see them in action.