Backless or Cosco combo HBB for 6 yr old?

[kater-tot82]

My stepdaughter is going to be 6 yo in March, she is about 44 inches/42 lbs. One or two weekends a month she goes to her biological mom's. Currently she is in a Cosco combination seat in booster mode. I noticed a couple of weekends ago that the lap belt on the Cosco seat seemed kinda high on DD's abdomen.
DD's BM is not interested in CPS at all. She wouldn't even replace a seat after she was in a car accident (hence the Cosco seat). I was wondering if a backless Turbo would be adequate in this situation since she doesn't really have any side-impact protection with the Cosco seat in booster mode. BM drives a very old car that is in bad shape and DD is outboard. We have a HB TB for carpooling and it fits DD great acros the lap portion. HB TBs have gotten so expensive so DH really doesn't want to pay $60 because BM is so irresponsible w/ seats and basically they get trashed with food, etc, and that's another reason he doesn't want to lend out our carpool seat. I was thinking maybe a backless Turbo would work?
So, bottom line: Backless Turbo or keep her in the Cosco seat? Or maybe that one Cosco backless booster that is like $18 at Walmart? Or some other (cheap) alternative I am missing out on? Or is a backless less than ideal? I don't think her head is above the seat yet...
ETA: Obviously we do not want DD in any danger so we will do what it takes to keep her safe. She is just w/ her BM so rarely that we don't want to invest a lot of $$ for something that'll be treated like crap--but BM won't buy a new seat. The responsibility falls on us.

 

[Maedze]

I would rather see her in a backless TB (don't forget the screws in the armrests!) that provided an excellent seatbelt fit than a Cosco combination seat that provides a poor seatbelt fit :twocents:

Of course, ideally, a 6 year old would be in a high back booster with excellent side impact protection, but the most important part of the booster is the fit of the seatbelt, so the TB wins, even if it is backless.

 

[tanyaandallie]

Does bm vehicle have headrests? If so, then a backless would be fine. If not, then you need to make sure she has head support from the vehicle seat before you put her in a backless. Depends on the car and how tall she is.