In order to reduce polishing costs and correct unexpected errors in fabrication and polishing, the support of very large optics can be actively enlisted in telescope mirror optical figure adjustment. A set of leaf springs is used by the Keck Ten-Meter Telescope to apply moments about the pivots of the mirror mosaics' whiffletree support. The springs successfully reduce the polished rms surface error by a factor of 6 to 15, while reducing the 80-percent enclosed energy diameter by a factor of 2.5-6.0. Additional current limitations on figure improvement include the difficulties of polishing higher spatial frequencies and predicting warping during mirror fabrication.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.