Torsional loads make the pinion rise. If you load this thing it's going to make the 4 bar set change instant centers as the bars torque and pull, thus changing the "original" centerline of your instant center for the car. I always recommend 2 degrees of down ward (and this only a recommendation). I can't not be hands on to see it so I only recommend 2 degrees. Adjust bars equally so as to not disturb the instant center of the bar angles. Does your tranny have a downward angle? Vibrations will ocur when the two intersect points (Trans and pinion intersect points) are varied as such with pinion downward, tranny downward. Be on the safe side and get the tranny to point directly at the pinion. A couple maybe slightly in a degree angle up above the pinion intersect will get you a smoother operation and allow for the pinion the work the bars under load.