My DD started rolling over onto her tummy to sleep from about 6.5mths, right after a friends baby passed due to SIDs. DH and I were totally scared about it, would turn her over and in doing so wake her up.... but she always turns her head to the side and now she won't sleep in any other position. It's usually on her knees, bum up, but sometimes it just spread eagled, and never under any covers (so I am starting to layby suits now for winter!!!!)... it so cute. I would say settle him on his tummy and see if it will suit him more...(just keep an eye out like we did for the first few weeks!)