3dplane -
*IF* my center-of-camber selection is correct, then I would make the claim that the angle is too steep and the airflow is not staying attached :
I agree with Weather Spotter that a longer kamm-back would be better, but I also think that if you get the angles right, it should still be a net benefit. I think that aerohead had a table of "diminishing returns" of a boat-tail. Obviously a full boat-tail would be best, but pragmatic concerns make it necessary for ecomodders to figure out how far they want to go.
But I'll let the real aero-experts chime in.
CarloSW2