The present invention is directed to mitigating overuse of limited membrane regions in electrochemical conversion assemblies, particularly under cold start conditions. In accordance with one embodiment of the present invention, the anode and/or cathode flowfield plates of an electrochemical conversion assembly are configured such that the fluid header region defines an anode fluid header, a cathode fluid header, and a coolant fluid header configured such that a feed region of the plate defines an array of substantially linear fluid channels extending from an acutely angled header/feed interface defined on the plate to a feed/active interface defined across the entire active area of the plate.