My little girl is 2.5 years old with Down syndrome, hypotonia, CAVC repair, profound bilateral deafness, and vasomotor instability. She is 21 pounds and 28 inches tall. We have a britax marathon and Graco all in one. We were advised to FF her due to her deafness and her vaso motor instability. Our issue is now that she is FF we are realizing she is desatting into the 80's when she falls asleep and maintains the mid- 80's until we hit a bump and she readjusts. Then as she falls back asleep and relaxes she desats. again. I can see that her head slumps to the side when she is asleep and have no idea how to fix this. We are looking into seats but can't settle on one. We drive a Ford E-350 Passenger van with a bench seat and a 2013 dodge dart.