Another thing it took me a while to realise is that it is possible to have the bottom rail too tight.
That's definitely where I was going drastically wrong - every time she felt insecure I just pulled that rail tigher! Lucky she's a patient little thing though with all the pulling and hoisting I'm putting her through. I'm sure there are plenty of parents and grandparents having a good laugh at me doing my little sling dance in the car park each afternoon at school ;-)