The R E seems to have plenty of raw torque to handle more gears. If it had a still higher gear than the fifth one, or if the fifth one were made higher, then it would seem to have the torque to handle it just fine. It wouldn't have to be that much higher to handle an additional ten miles per hour speed. At a time like this I wish I knew what I'm trying to talk about! But someone on the forum may have that sort of knowledge - hope - hope!!!