a structure including a flow field having a first plurality of channels at a first edge portion of the flow field, a second plurality of channels at a second edge portion of the flow field opposite to the first edge portion, and a third plurality of channels between the first plurality of channels and the second plurality of channels, each of the channels having an inlet end open to a header in fluid communication with the inlet ends, the header including a first restricted flow region configured to decrease fluid flow to the inlet ends of the first plurality of channels relative to the third plurality of channels, the header including a second restricted flow region configured to decrease fluid flow to the inlet ends of the second plurality of channels relative to the third plurality of channels, and wherein the structure includes one or more cross passages configured to increase fluid flow to at least some of the first and second pluralities of channels at the first and second edge portions of the flow field relative to the third plurality of channels located between the first plurality of channels and the second plurality of channels, each of the one or more cross passages extending from a respective location at the inlet end of one of the third plurality of channels where the inlet end of the one of the third plurality of channels meets the header, and away from the header and toward one of the first plurality of channels or one of the second plurality of channels.