My guy is suddenly 44", but his head has been partially above the top of the Volo seat since he was 42". Long torso. If he really falls asleep in it, it's just barely supporting his head, and with this suddenly inch he got, I'm not sure if it'll be good for him at all.
Regarding storage space, it's not big, when the kid is in the seat they take up part of the space b/c the seat goes further down, and there's a weight limit for the basket anyway.