High weight, but no alternative

As we travel a lot and we did not want to sit in the car for 3 hours in a baby car seat, our daughter, we decided on this seat. The "Buckle up" is somewhat complicated, but once you got the hang of first times out, it is no longer a problem. He is also very hard, even without a child, so I just let him in the car and not (as with a lighter baby carrier for short distances, for shopping, to the doctor, etc.) take out. But since we have not found any alternative that our child in a lying position, so spine-friendly, three-point belt with secure (some have only lap belts!), There was only the Romans left. I do not regret the purchase, soon my nephew is in it and after my second equal sunshine.
My daughter was up to the 4th month of life in it. Then it was too tight.