As per the email I received today: Models 2008 and newer have a replaceable tether. I have the pdf and can send it out if anyone needs it. Just message me.
The CDN manuals have been updated to say that the tether is mandatory.
From my CDN manual pg 22 and 24.Forward Facing Installation Step #1 (Bolded in Red) Always use top tether...It's a little deceptive because it does only say recommended under the actual tether section.I just uninstalled my Radian to look at the tether and I'm not convinced that's a replaceable part. I'm going to email my contact at Diono in the morning because if it is a replaceable part I want her to tell me how a parent would do that, and I'm going to mention the...
My 4.5 yr old is 37lbs and RF in a Radian. We're going to have to turn him soon because he's outgrowing it by height but it's gotten him this far. This is the kid that was 25 lbs at 8 months and then held steady at 33lbs until last November. I think you'll be fine with a Radian.
If you want inexpensive combination seats there's also the Maestro for about $129. It will harness to 47lbs, but be outgrown by height around the same time as weight so you'll have to buy a booster.
There's also the Graco Nautilus, it harnesses to 65lbs, then converts to highback booster, then lowback booster. It's about $229, unless you can find a really good sale.
Some companies have the 1" rule, some companies have a stated height limit. I would not advise you to go against the manufacturer's recommended use for the seat.All Canadian Radians harness FF to 65 lbs.My 4.5 yr old is riding RF in a Radian Premier in our 2005 Honda Civic. He's 37lbs and 42".
I would also check out the True Fit. Be aware that the Complete Air must be installed on 45 degree angle no matter what the age of the child, so it takes up a lot of room front to back. It also has a 36" RF limit in Canada.
My 4 yr old is still RF in a Radian. He's 37lbs and 40 in. He doesn't mind having his legs bent up a little, although I mind when he's back there kicking his brother. You can PM me your email address if you want to see a picture.