Forgive me if I mix terms, please ask me to explain a little further if this makes no sense at all.
Could you take a bipolar reactor and split the stacks up with dividers as you would in a unipolar set up? Employ the same "channeling" idea that Bio showed us in his latest video on his beast dividers. Only instead of carrying 2 separate electrolyte sources the channels were connected to simply carry electrolyte in evenly across all stacks and give the gas a faster way to exit on top. This seems like a way to reduce the restrictions on any electrolyte flow and still keep things nice and cool.
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If i'm off in left field that is okay, i'm simply trying to find ways to balance the flow of water and then give the gas a quick way out of the reactors.
Pictures are not yet available unless you want a picture of the side of my head where this idea currently resides.