Systems and methods including a header flange to evenly distribute contact pressure across seals include, in some aspects, a plate including a bead and a flange edge. The bead includes a bead-side and a bead-corner. The flange edge defines an aperture through the plate. The flange edge also includes a first edge-portion proximate the bead-side and a second edge-portion proximate the bead-corner. The bead-side and the first edge-portion define a first edge-distance therebetween. The bead-corner and the second edge-portion define a second edge-distance therebetween. The second edge-distance is greater than the first edge-distance.