I think I'm probably being a little obsessive, but...

A has three boosters. A compass in dh's S10 truck. She rides to school in this in the mornings only. All right turns and doesn't cross any big intersections. It's less than a mile. Currently, in our main vehicle (Jeep commander) she is riding in a Vivo because that is her preferred seat. She's leggy and even though the seat is somewhat shallow, it angles down and she can still rest her legs on the seat. In my MIL's car, whom she rides with only one time a week on average, sometimes two times, she is in a Monterey. The trips are longer, through intersections and narrow roads. The car is a Chevy Cavalier and because E's seat is also in there, they each are outboard. Now, here comes the obsessing. It stands without saying that the cavalier is definitely not the safest vehicle. I feel like that of her three boosters, the Monterey provides the most side impact protection, and felt like MIL's car was the best place to put it. I took into consideration the routes, the cars, and her preference for spending most of her riding time in the Vivo.

Here's the problem. If she grows, even just a smidge, the headrest will have to be raise enough that the seat will no longer fit outboard. The roof of the cavalier is just too low on the sides, and the wings of the Monterey just too massive. It would still fit center, but center is not doable with E's seat right next to it. I haven't tried the Vivo, but I'm thinking it would probably buy her some time before having to go backless, which I desperately freaking don't want her to have to do in a cavalier.

So I guess my question is if I am really losing that much protection if we switch the Vivo to MIL's car? It's possible that the Monterey would fit backless in the center next to E's seat.

So, which is the better option here? Outboard in the high back Vivo, or center in a backless (if it would even work)?

the vivo would be safer than a backless Monterey, if that's what you're asking.

Also, I'd check and see how she fits (keep in mind I'm not remembering how tall she is) in just the seatbelt in the center because the cobalt is the updated version of the cavalier and Jeffrey (and Damian did before him) passes the 5-step test in the center seat (ONLY the center seat) of our 2-door cobalt... of course, I chose to let him ride there now that he passes for more reasons than just boosters fitting or not fitting (his brother needing the head support, it being easier to buckle his sister when she's outboard in her booster and the oldest and youngest fighting badly when next to each other, along with only riding in that car like a handful of times a year)

We have a Cavalier and a Vivo and a Parkway. We don't have a Monterry, but have the problem of the Parkway hitting the ceiling outboard well before its max height. I think the shape of the Vivo will allow more growing room based on how it fits in the Cavalier. Unfortunately, I don't have a shoulder belt in my center seat so center booster is not an option for me. If you have or can buy a Radian, you should be able to fit a Radian outboard with a booster center, although I'm not sure if the Monterry could be that booster.