If you have GCEA strings for baritone, like HoldinCoffee mentioned, it is ok to tune it that way. If you are using regular DGBE baritone strings and tune up that many steps, it will put a good bit of strain on some part of it. When I first started learning, I didn't even know the baritone tuned different than the others so I tuned it GCEA. There is a little separation at the neck and body now. I don't know if it is because of the tension or if it was already that way, but I'm sure that amount of tension wasn't good for it.