How different to hear a boxer wanting to gain weight Personally, if I were 6'2" and @ 150 pounds (if a stone is @ 14pounds) I'd go with it.(for the record, I was once 6'3" and 155 before settling in comfortably at 178-182) Go to the gym and learn your craft, hit that heavy bag, do pushups and isometric type exercises. Take advantage of your height advantage, and please belive me when I tell you that proper punching technique- given the tremendous leverage your height allows- will pump your punching power far more than 15 more pounds.
The thing is, learn to use your body now, learn the technique now. Your body will look after itself and get to the weight it should be at soon enough.