this morning I found my 9 month old LO one her front in her cot. I rolled her back over, went to the loo and when I got back she had flipped back onto her tummy. Obviously she's more comfortable that way, and I've read that once they can roll on their own it's fine for them to sleep on their fronts, but I'm a bit concerned about the sleeping bag. Is she safe on her tummy in a grobag? I'm worried she's less able to manoeuver herself around...