My opinion? I would return the 3 in 1 and get your money back. Unfortunately, 3 in 1 seats will NOT be the last seat you will ever own. The majority of children outgrow the harness WAAAAY before they are ready to be in a
booster.
There are several higher weight harness seats on the market today.
Britax Marathon/
Boulevard/
Decathlon--all will harness to 33lbs
RFing and 65lbs
FFing.
Evenflo Triumph Advance---harness to 35lbs
RFing and 50lbs
FFing.
Fisher Price Safe Voyage Deluxe (they have discontinued this seat due to low sales)--made by
Britax--will
RF to 33lbs and
FF to 55lbs.
Recaro Signo/
Como--these seats are pretty large, so they may or may NOT work in your vehicle--they will
RF to 35lbs and
FF to 70lbs.
These are smaller seats, BUT will only harness to 40lbs.
Safety 1st Uptown--
RF to 35lbs and
FF to 40lbs
Cosco Scenera--
RF to 35lbs and
FF to 40lbs