A seal assembly for a regenerative heat exchanger can include a primary sealing member with a mounting base and a flexible contact portion that defines a first distance between a proximal edge of the mounting base and a contact edge of the flexible contact portion, the first distance being generally constant along the length of the primary sealing member. The seal assembly can also include a second member with a mounting portion and a cantilevered portion that defines a second distance between a proximal edge of the mounting portion and a distal edge of the cantilevered portion, the second distance being generally constant along the length of the second member. The first distance is greater than the second distance by a predetermined amount so as to limit the preload flexure of the flexible contact portion against a sector plate of the heat exchanger when the seal assembly is installed in the regenerative heat exchanger.