Volvo built in booster seats?

[Juliecloud]

What are peoples opinions on the Volvo built in booster seats? How safe are they?

[Cantstopeatingchocolate]

I've only used ours as a last resort, and only with at least one adult next to DS. I felt he's a bit 'perched' on it and it isn't really as safe as a proper booster. My DS is only 6 though. He's 127cm so tall enough for a backless booster but I prefer him in a proper seat.
As I said we only used it when we couldn't fit too 'larger' adults AND a car seat in, and second time when he was sick all over his car seat.