Very good design you've got there
Only got 2 things to point out that youve probably already thought of; im thinking that the water flow will be a bit restricted at the points below? 3 channels (only outlined 2 each side - oops) meeting at 1 point can't be good for flow. Perhaps sacificing some fin area for more space at the edges would be a good idea?
I also find the tapered inlet to be a sound theory, just as long as you taper for the entire length of the inlet, having the smallest part of the taper as the opening.
Other than that, it sure would be a good performer!