You might consider making some reverse scoop type -16's that have the opening face backwards. That way they would suck air via venturi effect but not shoot water out. Of course they may continue to suck air you don't want after on plane too. And anything like that should be really short to minimize cavitation at speed. You might have to make and weld into plate to get them short enough. May not work, just a thought.
I do think the big long 45º's you have will not work well with water passing over that area at speed.