How to keep 2yo safe when using car seater only

[MeeWhoo]

Hello,
I have 2 Concorde Transformer XT pro for my 4yo and my 2 yo.

It's been very good for the 4yo who is small and very slim, as his shoulders were very narrow for a 3 point system so he could wiggle his torso out very easily, hence, he was much safer with the "table" as a restraint since he couldn't get out of it at all.
Dd, however is tall and heavy. She is 17.3 kg at 2 and a half, so we could have already taken the "table restraint" off, but she is not safe at all using only the seatbelt as she just gets out of the top half within a second and just doesn't understand that she shouldn't.

She is actually not really safe with the table inset either as if she gets angry, she can tip it upwards so it ends up facing the roof of the car.

Any suggestions on how to make her safe that don't involve buying another car seat?

Sorry the title doesn't make any sense, I meant in a seat that uses the car's own seatbelt only.

Would something like this help? I also have a few friends with SN children who have bought a 5 point harness you can fit to an existing car seat or use on plane etc, but I think they are quite expensive. We looked at the seats with body restraint for DD, all the Which reviews using crash test dummies said they were fab, all the parents with an actual child said they were out of them in seconds.

Probably a silly question, but are you pulling the seatbelt really tight around the impact cushion? I have one of these car seats and my 4 year old cannot get the cushion move at all even when trying and in a right old temper.

Thanks Milloarmadillo, I will have a look at those I just hope they are not too difficult to put on because she is really strong and it's already very difficult to get her in the car when she is not in the mood.

Roughmagic, my 4yo ds can't get out of the table restraint because he is narrow and actually a pound or two lighter. The problem is that she is fat around the hips and belly so the inset already can't go very far in under the armrests, do then she just has to push a bit with her hands to dislodge it upwards. (see picture).

Anyway at the rate she is growing she will reach the upper weight limit within less than 6 months, I reckon...

There isn't really a safe option apart from buying a new seat. Apart from the fact that a 2 year old, as you have discovered, just doesn't understand that they have to sit still and upright in a high backed booster when the seatbelt is over them it's also not safe because no matter how big and heavy she is her pelvic bones just aren't developed enough for the seatbelt to hold her in place if you crash. this explains why

You need a seat with a 25kgs limit 5-point harness. So your choices are Britax Advansafix II, Britax Two Way Elite, Diono Radian 5 or Cozy n Safe Excalibur. They are all forward facing, there are plenty more if rear facing is going to be an option.

Thanks AliceMum09, that is very useful.

It seems that we shouldn't have bought both children the same seat as, at that point, we were really going with our experience with DS who, as I mentioned, is slim and narrow and so was safer with the inset than with a harness, and, it appears -although we didn't know this- only reached the weight limit after having reached the age one.

It is disgraceful that manufacturers are allowed to sell these seats and give them 5 star ratings -and charge quite a lot of money for them- without any mention of age as well as weight! DS is pretty small so I reckon most of his school peers would have reached the weight limit with this particular carseat before the recommended age (a lot earlier if the parents were looking at the lower weight limit for getting rid of the inset, which is only 15 kg!)

If anyone can recommend a reputable online retailer that ships to Europe I would be very grateful!