I would say @ 5 mo that is ok, he is still a puppy after all. Keep working with him. After he reaches 6 mo or so you can start to formalize OB, and start to inforce a higher standard. I would suggest getting yourself a longer check cord to work him on, and keep him on it for now so you can inforce all commands. Go to Home Depot or Lowes and buy 110' of poly rope for about 10 bucks and put a clip on one end, instant check cord! Make sure he is well socialized, and train around distractions often. Trips to pet store, crowed parks, busy streets, are all good for that. Good Luck! Keep us posted.