dim question about stage 2 car seats with no integral straps

[kitbit]

I need a stage 2 or 2+3 car seat for ds who is about 16kilos. We have seen some that have their own straps so you anchor the seat with the seatbelt as for a stage 1 seat, then the child uses the seats own straps to hold them in.
But we want one with a decent headrest as ds often falls asleep in the car, and all the ones with their own straps have rubbish rests that mean ds would flop sideways too much .
The ones with good headrests don't have their own straps, but use the seatbelt to go across the seat and child together.

Here's the dim question - does this mean that the seat is totally untethered, and in a collision if the child is thrown forwards surely the weight of the seat will push the child harder into the belt and cause more damage? Is that how they work or am I missing something really obvious?

cheeky bump
help!!

I dont think the seat really moves forward, once the belt is around it and the child, it doesnt really move. They normally have some sort of clip at the shoulder too, which sort of holds it all in.
If he falls asleep a lot though, these won't be very good as they don't recline. You'd be better off with a proper stage 2 rather than the stage 2/3.
My dts have only just gone into a stage 2/3 at 2 and half. I don't like the idea of just a belt for a toddler - mine would have escaped anyway. They still have a five point harness in their new seats.

good point about the escapability and integral straps, but the stage 2 ones look quite small still and I don't think it would last that long.
Are there any 2-3 ones that do recline do you happen to know (or does anyone else know?!)

The Britax Evolva 123 has a recline position, but you can't change it once the seat is fixed in the car. Has good head and side support though.

They hold the seatbelt in the right place so it doesn't damage the child's abdomen or neck. They also stop whiplash and things by having side padding, that's all. I think stage 2 is safer if the child still fits - once his head is above the top edge it's too small.

but does anyone know what stops the seat from shooting forwards in a crash and squashing the child against the seatbelt?