Thought I'd share a funny story here. I've been riding with my 18 month old daughter in the IBERT carrier, and she seems to have a lot of fun with it. Well the other day we were riding and she starts looking down at the gears. This isn't abnormal, so I think nothing of it. Well, 5 minutes go by, and she's still looking down. This is when I realize she FELL ASLEEP!!! She slept the entire 15 minutes home. It was a nice warm day, and I guess the seat is comfortable.
My little one often falls asleep in the ibert. It's only a problem when his head flops back and forth between my arms, making it difficult for me to steer. I generally really enjoy the ibert, but when he falls asleep I wish I had a rear-mounted seat with head support.
Mine fell asleep on her first ride. It doesn't look like it should be possible, but I guess when it's nap time, it's nap time. Even worse than her head laying back when she's asleep: When her head is thrown back, screaming and flailing in protest, because she doesn't want to leave the playground yet!