I had a ton of trouble finding a booster seat that worked well in the model 3. Lots of them fit, but it was easy for them to slide over the recessed buckle in the seat. Then my daughter (6) wasn't able to buckle herself in, and I'd have to shift the seat. (Which probably wouldn't do great things for my interior long term.)
After much research and trying several alternatives, I'm really happy with the Diono Everett NXT.
It has a rigid latch system that keeps the seat from moving, and a very narrow base, which makes it easy for my daughter to buckle up. It is top safety rated, has highly adjustable side impact protection, keeps the seatbelt very accessible, and does a good job of keeping her comfortable when napping.
(If your booster doesn't have latch, you should make sure that it is buckled in when not in use. Otherwise, it could fly through the car in an emergency situation.)
On the downside, it isn't cheap for a booster. It doesn't have any kind of cup holder, etc. built in. And it doesn't convert to a backless booster.
Everett NXT - diono® United States of America
"Suitable for children who weigh between 40 and 120 lbs (18.1 – 50kg) and whose height is between 38 to 63 inches (96.5 cm – 160cm) or approx. 4 – 12 years." (Note that your child must be able to sit with the belt at the appropriate location on their waist, and not move around / escape from the belt. You'll need a 5-point harness until then.)
I have no relationship to the company other than being a happy customer.
After much research and trying several alternatives, I'm really happy with the Diono Everett NXT.
It has a rigid latch system that keeps the seat from moving, and a very narrow base, which makes it easy for my daughter to buckle up. It is top safety rated, has highly adjustable side impact protection, keeps the seatbelt very accessible, and does a good job of keeping her comfortable when napping.
(If your booster doesn't have latch, you should make sure that it is buckled in when not in use. Otherwise, it could fly through the car in an emergency situation.)
On the downside, it isn't cheap for a booster. It doesn't have any kind of cup holder, etc. built in. And it doesn't convert to a backless booster.
Everett NXT - diono® United States of America
"Suitable for children who weigh between 40 and 120 lbs (18.1 – 50kg) and whose height is between 38 to 63 inches (96.5 cm – 160cm) or approx. 4 – 12 years." (Note that your child must be able to sit with the belt at the appropriate location on their waist, and not move around / escape from the belt. You'll need a 5-point harness until then.)
I have no relationship to the company other than being a happy customer.