Is there anything on the market to extend a 5 point harness?

[Jojay]

Ds1 (3) is in a group 1 carseat. He fits into it well. eyes are below the top of the seat etc, but the harness is becoming really tight to do up, especially if he has a coat on.

I don't want to take him out of this seat too soon.

Is there anything out there that can solve my harness problem?

[Brachy]

It is best not to keep the coat on whilst in the car seat. A fleece coat would be less bulky or just a blanket over him until the car warms up.