I tend to agree with the alignment shop. On a car that has adjustable everything on the suspension, changin the camber also effects the toe and the ride height. So, adjusting one thing has an effect on all of the others and that means to really get it right it is going to take quite a bit of time. Others who go and change the camber by simply adjusting it in or out don't realize they are affecting the other settings. BTW, 2.5 degrees is a LONG way out. After having the (a) shop double check that reading, I'd ask them to determine what happened to your suspension and then put a mondo alignment on by an experienced guy.