My son is 6 1/2 and is about 44/45 lbs. Height, I'll get back to you but when is a child ready for backless mode? He is currently harnessed in my car in a 5 point but in DH car, he is in a Graco Turbo booster with the highjack. DH keeps saying his head is above the seat so...
Mama to two wonderful boys DS1 (May 2007) and DS2 (March 2011)
I wouldn't put a 6 year old in a backless booster for everyday use personally. If your son's head is above the top of the turbo booster's back you might need to move the headrest higher. If you do adjust the headrest to a higher level you should ensure that the seatbelt fits him as outlined here:
If you posted this in the family safety section you'd probably get some good answers.
my almost 6 year old is still in a 5 point harness. In an pinch, I'll let her ride with just a booster, backless or otherwise, but not for every day or as a routine. My boys (at 7) were in a backless booster in one car, but have their regular boosters, with backs, for in the van.
I was under the impression that the backed booster was for fit, not because one was safer than the other, assuming that the child fits in both. So, if, at 6, your child fits properly with just a booster, I don't think there's improved safety between the backless and the regular booster. There is improved safety with a 5 point for as long as it fits. That's my understanding, anyway.
Sometimes with a younger child the shoulder belt can fit a bit better in a highback booster vs a backless booster, and although there are no standards for side impact protection, IMO it stands to reason that a highback booster with headwings/side wings and added eps foam will provide more protection than not having a back at all. To me this is important for younger/smaller children. All vehicle passengers should also have support to the top of their ears (adults get this from the vehicle seat back and headrest), however some backseats have low seat backs/don't have vehicle headrests in all positions. A highback booster can provide this head support for the child provided it isn't one of the brands that requires vehicle head support as well.
My 7 year old is in a high back booster, I'm not sure of his exact measurements but over 52 inches and over 65 lbs. IMO the advantage to a booster w a back is the seat belt is guided and better positioned for a child. Maturity is a factor too. My ds does need the occasional reminder to always face forward and sit all the way back in his seat.