Chicco - MyFit

Unless he has a very long torso, there are a lot of harnessed seats that will fit a 42” kiddo, and a much taller child too, not just for the next month or six. I don’t mean to say this in a rude way, but it’s the Internet and tone doesn’t come through, so I’ll caveat it that way - 40lbs is actually quite far from 36lbs. He’s more than 10% under the threshold for booster usage - the very lowest threshold, not the threshold where he should be/needs to be riding in a booster.  Something like the chicco my fit can be used in harness mode up to 54” and is also convertible to a booster, so that would be a great option to keep him safe until he’s big enough and has the core strength and maturity to be a full time booster rider. 

Seconding this. I had a MyFit also and it's like 3 times heavier than a KidFit. We were happy with the MyFit in harness mode but when we converted it to high back booster, it's significantly harder for my kids to buckle compared to the KidFit. At this age, I would recommend the KidFit (if your kiddo was 3-4 then I would recommend the MyFit)

Absolutely agree. Used a car seat from day 2 for my kid straight out of hospital. Moved from carrying infant seat from Chiccco to convertible seat from Gracco and now finally on a Chicco booster seat now that he’s 9. The recommendation is to use a car seat till 10. And for heaven’s sake even if you don’t use a car seat, make the kids seat in the rear seat not front seat.