Hi Gilly

In a "three across" situation it's really quite hard to give advice, reason being, that without physically being there and being able to check the installation of each individual seat and also how they fit in to your vehicle room-wise, it would be impossible for me to give you the right information. While three across positioning for car seats IS do-able, obviously it depends on the car, and the car seats. I've not installed the car seats that you have, in the car that you have, so it's a bit of a toughy on my end.

Where in New Zealand do you live?

Bonnie

I'm sorry I really wish there was something I could suggest, but without physically being there, it's pretty tough to ensure everything is A-OK and safe. I would suggest going to some stores and looking at your options for what might likely have to be a booster seat if your 4 year old is nearing 18kg. If you want to put them in a booster, obviously it is an option, but you will of course have to use that in conjunction with a three point belt. If you want to harness past 18kg, there are SOME options, albeit quite limited. If you do get a belt positioning booster seat, make sure it is one that positions the shoulder belt reasonably close to the body, between the shoulder and the neck (not rubbing against the neck) and one which makes sure the seat belt is positioned nice and low across the pelvis. Some suggestions might perhaps be the Graco Rallysport (Baby On The Move) or the Milano (Baby City). There are of course more options out there, but those are a couple that are quite good belt positioners but it will of course, depend on the child and the vehicle.