Tiff was kind enough to lend me her HAB so that I can use it for Ruby (thank you again precious one!)

Now, thing is, that she's not even in it for a few minutes and she's slipping down....and I know it doesn't look right etc and needless to say doesn't feel right for either of us. I've watched the DVD several times and am doing exactly what it says.

What am I doing wrong? I'm just using the standard heart to heart hold. It all ends up getting a bit much when I'm trying to readjust it all the time and Ruby starts getting over it very quickly then!!!