[jschiller]

I would be cautious about the longer tailshafts as that leaves less length for the driveshaft. You would want a longish driveshaft to get good geometry on the u-joints for durability. ERA has a discussion on their web site as I recall. You may also have trouble getting the driveshaft balanced at a shop if it is really short. Too short and it does not fit in their balance jigs.