BIG wheelhop! Please critique my launch

Pinion angle is the difference between the centerline of the transmission's output and the pinion gear. The rear pointed up or down is fine so long as it isn't any different from the transmission's angle under power. Under power is the key... This is so the smallest amount of stress and wear occur to the Ujoints. It also uses the least amount of power to spin the joints so if it's way off, even without any vibration or other stuff, you will go faster. So you need to get your car level and on it's suspension where you can work safely under it. Put some weight in the driver's seat to be "you" and a full tank of fuel. Then use an angle finder or magnetic protractor on the ujoint flange on the slip yoke. take a reading. Then go to the side of the yoke on the rear and do the same. Make sure when you take readings the surfaces of the flange and yoke are parallel to the ground. The difference of those two is you pinion angle. When you goto set it, you will want to use shims under the spring perches. 4WD shops usually have them in 1° - 6° increments, I use Mr Gasket, Moroso, and Lakewood most of the time. For a street car I'd go 2° down. For a drag car with the typical factory type suspension I'd go 4° down. For a road race or fast (as in top speed and handling) car I may go dead even. All depends on the suspension and power level.