Thanks very much for your replies.
The Stick -
Are you aware that kidsafe no longer recommend add on harnesses? How big is the child using this set up? Either way, an extension is still makes life a lot easier when you do decide to go to the standard belt.
No, I wasn't aware that kidsafe no longer recommend add on harnesses.
I'm planning on getting it checked out now to make sure that we are ok with what we have done. Thanks for that info.
The child in this seat is 4 years old and 17 kgs. I'll feel much better if I have a professional check her out in the seat with the harness to tell us if they think it is the safest option or not.
Shell68 - thanks for that warning about the safety. If we do end up getting one, we'll be sure that it is only sitting high enough for us to access it between the car seats only.
Thanks all for the responses.