A stiffener assembly for use with testing devices is provided herein. In some embodiments, a stiffener for use with testing devices includes an inner member; an outer member disposed in a predominantly spaced apart relation to the inner member; and a plurality of alignment mechanisms for orienting the inner and outer members with respect to each other, wherein the alignment mechanisms transfer forces applied to a lower surface of the inner member to the outer member and provide the predominant conductive heat transfer passageway between the inner and outer members.