The Nextfit is even heavier and more awkward to carry than the Radian.

The market for lightweight, easy to install seats are very limited. The Scenera is okay, but beware it is a major PIA in many vehicles. The Coccoro has some tricks to installing it. There's 3 different methods of installing it.

The other thing with the Radian is that it takes a LOT of space front to back, which creates lots of problems in cars if you want to rear face. Plus then you also have to worry about carrying the boot around which takes up space in your carry on.

Have you looked at the Safety 1st Guide 65? Relatively light, compact (relative to other car seats) and cheapish.

http://safety1st.djgusa.com/en/djgus...at-cc078bjb--1


The trick is to practice practice practice in multiple cars if possible. A car seat might install easily in one car and be totally incompatible with another. If you are going to be using it mostly in taxis or rentals, then I would definitely practice before hand.

For older kids 3 and up, the Ride Safer Travel Vest is a good idea.

Also, if you are traveling with a stroller, just put the car seat on the stroller. That's what I do. Gate check the stroller and carry the seat on board.