You should only have to loosen them a half turn or so, just enough to relax the clamping force between neck and body.They're all out about 1/2" and the neck won't move. Am I just not pulling hard enough?
Can you move it in the 'wrong' direction? If so, and you can't move it far enough in the right direction, the holes are drilled out of place and so you'll need to make new holes per the above post.