What about the NiZn accu Type? Did anybody try one of these? They have the big advantage of having 1.6V which is closed to the standard 1.5. Capacity is around 550 mAh for a AAA cell, which is less than the the typical 800 mAh for a NiMH, but you should be able to use them till the very end. So it should be ok for at least 2h of driving i guess, with additional driving speed over NiMH accus.