ooh gosh, I know it's weight based, but the Maxi is nowhere near as supportive as an infant seat. My DD is an amazon child so really really tall (think the average 7yo and that was her at 3) and she didn't outgrow her carseat until 2. I preferred to keep her in there until she was 2. Even though the maxi is weight rated from 8, the infant seat should go to about 18kg I think?
It doesn't recline as far either from memory. A little bub wouldn't be in the head safety zone either would they?