I have not seen anyone recommend a Hollis wing. I have been looking at the Hollis Doubles Donut Wing. It seems like it would be alot easier to vent air from the wing in a horizontal position with a donut wing over a horseshoe type wing. Does anyone have any experience or opinions about this wing.
Have a look at the wing in the picture below LiteHeddeds post. As bubbles rise, when you're in horizontal trim, the wing isn't in a horizontal plane. The side pontoons wrap up the side of the tank. The lower arch is beneath the tank. When diving in a horizontal position no gas can pass through the lower arch.
Now imagine a line drawn from the highest part of the wing in the photo to the bottom of the wing, where the lower arch gos underneath the tank. When this line approaches horizontal, gas will pass through the lower arch of the wing. Now perform the same thought experiment with your doughnut wing of choice.
I'v found that it's not so much about horseshoes v's doughnuts, as it is about good design v's bad design.