Second seat option for SN daughter

I am looking for seating options for our 8 year old with SN. In my car I have the special needs car seat which is a snug seat pilot, but need to find a better seat for my husbands truck. Right now he just has a graco highback booster and it is just not enough support. I recently tried her in a friends nautalis and she just fit with the harness. I am willing to put out some money if it something that she can use for awhile? Insurance only pays for one SN caraway. . I have looked at the ride safer vests and I am wondering if once she is in is it okay to lock the seatbelt so she can't lean all around? Sorry for the novel. I am still also trying to figure out a solution for a plane ride that gives her better positioning for her lower half. She is tight which makes it hard for her to sit on regular seats without proper positioning. Okay now I am really done.

Welcome to C-S.org!

Are your DD's SN just positional/neuromuscular or also behavioral?

The problem w/ a vest is that even w/ the belt locked, kids do have a little more freedom to move around. If she really needs a harness, a vest may not provide her w/ enough restraint/support. It is something you could try, though.

The Britax Frontier 85 harnesses longer than the Nautilus. It would probably last her a couple more years and would provide more support than a vest.

If you're thinking a locked seat belt would be enough to keep her in place, though (vs a harness), you might look at the Diono Monterey, which is the non-SN version of the SnugSeat Pilot.

For the airplane ride, the FR is FAA approved. It may be a tight fit in some airplane seats, though (and it's heavy). The CARES has been allowed to be used in SN circumstances past the weight limit (I think you have to have a Dr. note or something like that w/ you). That would provide your DD w/ upper body support on the plane and then perhaps you could use rolled towels/blankets, clothing or pillows to help provide support on her sides (between her and the armrests).