Ally had one similar when she was a bit smaller. It worked well for her and didn't come undone. Her hair got in the way and it started to grow. It kept pulling her hair. I eventually went to this for both my babies and love it. Ally is just over 3 lbs and has been using it a long time. It's on ebay too.
http://i433.photobucket.com/albums/q...g?t=1245951084