My 6 month old DS is about to swap from his Moses basket to a cot in his own room. The only thing is he is an avid roller! as soon as you lie him down he flips to his front. hes been doing It for weeks and hasn't worked out how to get back to his back. what happens when he's in a big cot with lots of room? I'm worried about the safety of it in the night. anybody had any experience?