Just to be clear, the Coanda effect as I understand it is that a jet of air will stick to a spherical trailing edge so that the flow on the upper surface and lower surface meet somewhere on the lower half of the sphere, thus increasing lift. Unless something is wrong with the way I understand the effect, I think it only applies to the air exiting the surface.

Also, Coanda probably won't give any lift in a hover situation, since there is no foward velocity, so no airflow over the lower surface, hence no difference in pressure and no lift. However, since the air exiting the surface will be angled downward it will provide a little lift that way.