I have a RA55, I haven't gotten a chance to install it yet. I'm just wondering if this is an issue. When I've got it in for example the rf position, just sitting on the floor in my room, the back of the seat moves up and down, probably a few inches. Is this a problem? I would think once it's installed that will stop, since it will be against the seat, not the seat in front. That may be confusing.