I vaguely remember the magic angle being 30 degrees, not sure where I got this from but it *may* have been from the book 'baby on board' which is written by DD's paediatrician, who genrally appears to talk a lot of sense!

I think we used a towel under the matress and a couple of books under each leg - we tried yellow pages but they raised it too much and dd just slid to the bottom!

HTH