An optimized fluid valve port has the following features: 1) the seal is preferably a standard O-ring seated in a rectilinear seal channel of one of a first or second valve body, 2) the unsupported span of the O-ring during valve port crossing is limited to a length of less than approximately three O-ring diameters, the support being provided by a web disposed between port openings; and 3), within the area of the O-ring, the fluid flow area of the fluid valve port is maximized.