I have seen threads on this subject before. You might want to do a search. The advice seemed to be to tie the bottom of the bag to stop little one from wriggling too far down, if necessary.
Cheers
Pauline
------------- I have NEVER been lost, though I do admit to spending several hours locationally challenged
More tentage = Campus Sherpa 4 - reproofed and still going strong
In Memorandum = Vango Quest, Khyam Chatsworth, and a frame tent OH wouldn'try!!!!
We took Elizabeth camping at 6 months. She slept in a little mini inner tent of her own, next to us, that just popped up on its own from 'Little life' All the kids still play with it now even the 16 year old.