When to go from high back to backless booster?

I have a newly minted 7 year old who would very much like to ride in her booster minus the high back. We just had her 7 year old checkup yesterday and she is a tiny thing - 50 lbs and 46 inches tall. She is currently riding in a turbobooster and almost never falls asleep in the car unless we are on a road trip late at night. I told her I would ask the experts here and see what they have to say about it.
Thanks!

The most recent study on the subject found that there is no difference between highback and backless boosters "Importantly, these results suggest that the effectiveness of booster seats does not vary by the type of booster seat: backless or high-back." http://pediatrics.aappublications.org/content/124/5/1281.full

With that being said, they didn't really differentiate between a dedicated highback booster and something like an older model 3-in-1 highback booster, so maybe a difference really exists between certain highback boosters and backless boosters; plus, a previous study did find a difference.

Since your daughter is in a Turbobooster, you could always try her in backless mode and see how it goes, and if everything goes well, just put the back on for longer road trip drives where sleeping is a concern.

I know some people prefer highback boosters if there are no side airbags or sometimes highback boosters are preferable if it's a situation where there aren't headrests in the vehicle to provide protection at least up to the child's ears.

I personally like 7 year olds in highback boosters, at least as their main seats. My daughter is almost 8 years old (around 48" and 48 pounds), and I do let her ride in a backless booster as a spare in her grandparents' vehicles, because I know she's definitely going to be awake and only taking short rides. For my car, I prefer the highback for a full-time situation, mostly for the physical reminder of having a booster around her to help her stay in position on anything longer than 5-10 minute car rides. That's just my personal opinion; I'm sure there are others who are happy with backless boosters as full-time seats for their 7 year olds, and I hope they'll chime in, too.

My dd is 7.5 and has just moved to backless boosters in both of our vehicles.

I moved DD1 to a LBB at age 8 in my car. She still ride in a HBB PW in DHs truck, at her request because she still sleeps in the car (we usually take the truck on long trips).

Mine got to move to backless at age 8.

The only thing to add to what the PP's have said (that it's kind of a personal preference) is does she have adequate head support without the booster (tall seatback or headrest in the position that she sits).

My DD has been using a backless on occasion since she was 5. Still uses HBB in both of our vehicles on a full time basis (she's 7 and about the same size as your DD) and in our truck she'll be using one until we sell it because it doesn't have extendable headrests.

If my DD doesn't outgrow the back portion of her BigKid Sport by the time she starts 2nd grade, I may still go ahead and switch her to lbb mode then.

However, we also use the Frontier in booster mode for her and that's the seat we'll usually take on longer trips.

I also want my DD to fit without having to worry about the belt adjusting clip if possible.

OP here, thanks all for the advice. She has ridden without the back before in certain circumstances (vacation, car pool) and does absolutely stellar with it. She is a super rule follower so no worries there and she rides in a 2012 Highlander with side airbags so we do have that layer of protection as well as adequate headrests.

I think she was uncomfortable in the seat in the winter with so much extra bulk from clothes and jackets in the small space of the highback but that shouldn't be much of an issue now that warmer weather is here.

She has also been experiencing car sickness issues over the last several months and I'm wondering if not having the headrest portion of the highback surrounding her head would help with that.

She does not fit without the silly belt adjusting clip that I personally find to be a PITA, but it is her seat so.....

I think we'll hold off until the fall/winter at least and maybe try experimenting with taking the back off when she is feeling ill in the car.