Oh my, I seem to have reignited the airbag/tethering debate. hot button issue! Sorry about that
I believe everyone here has the safety of our children as their utmost concern and the issue is a disagreement about how to best achieve that goal. It seems to be a complex issue, likely depending on specific vehicles. I don't feel I know enough yet to settle on my own opinion and appreciate the input of all. Thank you!
No worries at all- Always a good idea to ask when the safety of any passenger is involved! This really is not a debate, but rather correcting misinformation. Some vehicles in the USA and Canada do indeed have sensors for the front passenger airbag deployment that can be affected by the downward and/or forward force of a rear-facing child restraint that is braced against the front passenger seat back. You must consult your vehicle owner's manual to verify if this is a potential safety risk.
For example, I am aware that GM, VW and Chrysler are all likely to have some reference in certain new owner's manuals that prohibit rear-facing carseats to be braced and/or tethered in certain configurations. I have not heard if Audi will do the same, as it is part of the VW group, or if any of these companies will make this retroactive to previous model years.
Thank you again so much to all of you who have taken your time to share your knowledge with me. I am grateful for the input from all!
Thank you very much for visiting! If you have any more questions please feel free to ask. Even these discussions that go a little off-topic can be very helpful to others reading so please don't worry about bringing up potentially controversial safety topics;-)
As your your situation, I would wait as long as possible to make a choice. Your Radians should allow you to continue rear-facing for quite some time and you can use the angle-adjuster if needed. When your Radians are nearly outgrown, you may find you are ready to move front-facing. Or, you might find you reached the weight or height limit much sooner than the other limit, allowing you to find a USA approved product that will work at much lower cost, perhaps one that can be used as a forward-facing seat and booster as well. Plus, there may be new seats available that have even higher ratings.
Honestly, rear-facing is so safe and the risks so low when installed and used correctly, I don't think there is going to be any significant difference in safety for your child as long as they are within the limits of the carseat.
For example, the Clek Fllo offers a very high weight limit and anti-rebound bar that avoids a rear-facing tether. While expensive, I imagine importing a high-end Swedish seat will be just as costly or more.
Amazon.com : Clek Fllo 2015 Convertible Child Seat, Drift : Baby
For a little less money, the Britax Boulevard Clicktight offers exceptional rear-facing height limits and will have an optional anti-rebound bar:
Amazon.com : Britax Boulevard ClickTight Convertible Car Seat, Circa : Baby
The Graco Milestone offers above average weight and height limits at a reasonable price and works as a booster as well:
http://www.target.com/p/graco-milestone-all-in-1-car-seat/-/A-16721763
All three are on our Recommended Carseats list at CarseatBlog as well.
Good luck with your choice!