Just finished evil chest workout with guy friend to keep him company. He\'s naturally tall and thin, and is trying to build muscle. He has a problem spot on his chest. He\'s got a bit of a sunken spot in the center of his chest he wants to \"pop out\". Any suggestions on how he can build muscle there, or make it less noticable? I really don\'t notice it, but if he gets a lot more muscle in his chest, it will be.