I have the same concerns, but not really how the baby will behave in J. More about how it would be to keep him in the lap in a J seat. He is too big for the baby bassinet, but too small and young for an own seat. Wonder if he fits side by side with Ms. if he (they) needs to take a nap. 21" should be enough? Anyone with experience of lap baby in J?
Or should I stick to row 41. Which has been great to travel with a baby in.