The least stressfull angle on a u joint is no angle. In other words the tranny u-joint and the rear end ujoint need to be on the same plane or angle with each other. In racing applications you normally point the pinion angle down about 2 degrees from the tranny angle so that when the rear end "wraps up" from torque the rear end u-joint and the tranny u-joint are @ the same angle/or on the same plane under full power. Lining them up (or point them at each other) .... sounds good in theory, but remember that angle is constantly changing because of bumps in the road, load weight, etc. Dunno' if that makes sence, or makes it more confuzzzzin' for ya'.