A retractable stern reaction frame for reinforcing self elevating platform cantilever beams. The preferred embodiment contemplates a support framework mounted on a self elevating platform transom and positioned to engage the cantilever to project the reaction point farther towards the cantilever reach. The frameworks are to be retractable (or portable) to allow the self elevating unit to position itself closer to the jackets than would otherwise be possible. The framework is designed to transmit the reaction forces back to the main deck, cantilever support bulkheads, inner bottom and bottom structure.