She is in the Hi Liner in DH 's car with adult seatbelt
That's what we are using currently also.

Olive- yes you need to take into account the 'boost.'
Does this mean with the 145cm, I need to look at what the boost of the seat is? Who was it that said H harness are dangerous? Research link please?
We have had him in the hiliner for not very long, he was way over the 5 point weight rating for our infa-secure booster which we hadn't even realised, but also outgrown the straps. I really want to import for my DD.