Recently identified fundamental classes of dual-mirror double-tailored nonimaging optics have the potential to satisfy the pragmatic exigencies of concentrator photovoltaics. Via a comprehensive survey of their parameter space, including raytrace verification, we identify champion high-concentration high-efficiency designs that offer unprecedented optical tolerance (i.e., sensitivity to off-axis orientation) - a pivotal figure-of-merit with a basic bound that depends on concentration, exit angle, and effective solar angular radius. For comparison, results for the best corresponding dual-mirror aplanatic concentrators are also presented. (C) 2010 Elsevier B.V. All rights reserved.