Backless booster ok for occasional use?

[XanaduMama]

I know this has probably been gone over a million times, but I don't have time to do a proper search.

ds is 5, 48lb and close to 50" tall. He's in a Graco Nautilus in our car, and will be harnessed to the limit of the seat. We're starting a new arrangement, though, where he'll be riding in another family's car once a week, about a mile. I need to get him a booster, but am really loath to spend a whole lot of money ($80 vs. $15-20) on a seat he'll use so rarely. What do you think--can I safely go with a backless booster over a HB booster in this situation?

[chel]

it really depends on the vehicle, but chances are he will need the back.

[chickabiddy]

It's legal for him to use a backless booster, and he's probably tall enough to fit adequately.  I really REALLY prefer to see 5yos in highbacked boosters, but a big 5yo in a backless is not misuse.

You don't need to spend $80 on a highbacked booster.  You can usually find a Graco Turbobooster for closer to $50 on sale at a big box store.

[XanaduMama]

He'll be riding in a Prius, if it matters

[MJB]

I'd get a high back Turbobooster for $40-50. That is a TALL 5 yr. old though! He probably would fit in a backless in most cars. My almost 8 yr. old is a few inches taller and still needs a back for the belt to fit in the third row of my Mazda5, though. 

[TiredX2]

I would look at the seat he will be sitting in in the car.  Does it have head rests?  Especially with him being so tall, there is a chance he will need the headrest on a backed booster.

[chickabiddy]

A Prius should have headrests in all rear seating positions, and a 50" child should not exceed them even in a booster.  I'm still not thrilled about a 5yo in a backless booster, but I think that it is likely not misuse.