Test the barrier. I have an Outback, and I borrowed the barrier that is made for that model. The dogs can wedge their heads in and push the whole thing out in order to climb up front. It is easier for me, and more storage capacity, to just use crates. I can fit two plastic ones side by side, a small one for Tallulah and a medium one for Tess. They are not large,but we stop and walk the dogs every few hours.
Also, if we stop for lunch, we can just open all the windows and sometimes the hatch and they have plenty of air. (we sit where we can see the dogs) I always crate the bullies when we stay in hotels, although Tess would sleep with me if she could, but she is too big
Tallulah will pace for hours unless crated, then she falls right asleep. It is a security thing with her. Crates are our friends!