Have to say with the benefit of hindsight I think tummy time is pretty pointless. My son had a very flat head on one side, but absolutely hated being put on his front and was inconsolable every time we tried. He was, however, upright a lot of the day in a wrap sling as he liked to be carried all the time, and I think this did exactly the same job as the tummy time, in terms of taking pressure off the back of his head and strengthening his neck muscles. He's now 10 months, turning himself onto his front at any opportunity and crawling around happily, and while his head is still a slightly odd shape it's much better than it was. I think if I had another baby that hated being on their tummy as he did, I just wouldn't bother.