When its installed on the bike, the iBert feels a bit loose and flimsy as the stinger does not snuggly fit into the seat. But after a child sits on the iBert, you hardly notice the wobble.
I had no problem fitting Bea to the seat. She was comfortable almost immediately. The problem was fitting the Giro Me2 infant bike helmet on her head. It irritated her and she kept on removing it.