A sag-bending system is disclosed. The sag-bending system comprises a sag-bending glass support mold and a perimeter thermal manager. The support mold comprises a plurality of rib members extending in a first direction, each of the plurality of rib members having a curved upper surface shaped to form the collective upper surface having a position and shape to support a quadrilateral-shaped sag-bent glass sheet into a desired contour, each of the rib members further having a lower surface, and a plurality of support members extending in a second direction between at least two of the plurality of rib members, the second direction traverse to the first direction. The perimeter thermal manager is sized and positioned to surround, to extend at least partially over, and to extend at least partially under the periphery of the support mold.