First, where does Frankie sit in your car while you're driving?
He should always be seated in the rear of your car.
Always restrained in a car seat harness and always sitting in a secured booster car seat.
If you can place the seat in the center of your back seat that should be the best location for the least amount of jiggling while driving.
The fact that these booster seats (see link below) allow your pet to sit high up enough off of the seat and the foam is so dense...makes for a more stabilized drive as well.
Plus, they can actually see out the passenger window so...my dogs love to see what's going on out there, too!
The seat covers come in a variety of colors & fabric types and they wash up beautifully, too.
Also, it helps to not feed your dog prior to travel time...just in case.
Here is a link to the best pet car seat in possibly the world...
http://www.snoozer-dog-beds.com/dogcarseats.htm
I own three of them and each one of my lil' barfin' dogs...ceased the yucky habit the day they took their first rides in these!
Hope this info is of help!