6.5 on short arms . pinion angle problem

i set the lowers at 17 inches and the wheel is centered in the wheel well so thats cool . the uppers were set at 15 5/8ths as per chart i seen on yucca man . now the pinion angle is to low for the front shaft not to vibe . how much caster can i run without having an problems ...i have plenty adjustment on the upper arms and was just wandering how far i should adjust them . everyone says the ride with 6.5 with short arms is shit but it rides better now than it did with stock CA's and a BB . but anyhow if i use an angle finder on the front pinion what should i adjust it to so i wont have vibes and weird tire wear . just looking for advice from some people running short arms 6.5 . thanks for the help in advance ...

place a large socket that just fits over the top of the upper balljoint, it should sit flush, then put the angle finder on that. LEVEL GROUND!! Some say putting it on the flat of the bottom of the knuckle works too.

As for the angles, Post up pics, pics with the angle finder on stuff. I would start off with about 5 or 6* postive castor (top of the Inner C tilted toward rear of jeep), drive it, readjust, drive it, so on. Steering will get worse as you correct for pinion angle vibes.