I have that very angle finder actually, so just stick it on the top of the upper ball joint eh? Man i read all sorts of stuff talkin bout droppin a plum line through the balljoints holes blah blah... i'll look at it this afternoon!!!

 

it would prolly be more accurate, but to check caster roughly the angle finder should be fine, cause if your top ball joint isnt in line with the lower then you got bigger problems then caster