And to think that you guys bought arms. You should try making them! Oh btw, an easy way to get a baseline, is to set the center of the balljoints where the factory ones go. Just need to add 2" from the frame to the balljoint center (becuase of extended arms), and measure from the front of the foot peg to the center of the balljoint. Get those two measurements correct and that is basically the stock alignment settings. You'll have to fine tune camber, but the caster setting will be correct. Also, make sure that you measure not only a straight line from the frame to the center of the balljoints, but, that you measure at an angle from the center of a particular bolt to the b/j center for the lowers. From there you can fine tune your caster to make it turn easier or harder. And remember, adjust caster 1st, camber 2nd, and toe last.
Positive caster is when the upper balljoint is positioned behind the lower balljoint. Negative caster is when the upper balljoint is in front of the lower balljoint.
Positve caster is better for straight line drivability, but makes it harder to steer.
Negative caster makes it easier to steer, but can make it too twichy in a straight line.