I just found this seat that has a "higher weight internal harness"…. the Safety 1st Apex. Now, before anyone goes on thinking I’m promoting this seat… *I know nothing about it except that you can use the internal harness up to 65lbs, just like Britax seats, and its less than half the price. I know nothing about its safety ratings.*
Up until recently, I thought only Britax made the seats that allowed the harness to be used up to 65lbs, but now I’m finding quite a few more (found them on this site). P is only 25(ish) pounds right now, so we still have 15lbs before he outgrows the harness on his Alpha Omega. But, at least I now know there are cheaper alternatives!
And… a video for you. A crash test with a 10 year old carseat.