I've got DS in a Peg perego infant seat for now, until I can get my new radian, and when I told DH we needed to get the radian with the next check, he said, 'but you only have him on the 2nd slots' which is true, I only have the straps of the infant seat in the middle slots, the cover is funny, and pulls the straps up once they come through the shell, I have to stick my finger deep inside to see where the next slot is in the shell, and the cover would put the strap from the top slot waaay above DS' shoulder. so DH's question is, is it possible to outgrow an infant seat by height, without ever using the top slot or should I be using the top slot anyway? His head, depending on how relaxed he is is between 1 and 1/4 inch and 1 and 1/2 inch from the top of the shell, the cover sits another 1/2-1 inch above the shell, and I can't get it down, the slots in the cover are very stiff, and tightening the straps doesn't pull them down either, the middle cover slots are now even with DS' shoulder