[QUOTE=maddmaxx;8571112]My own preference for a hitch rack is one where the tires of the bikes are supported in tray's and the bike is held up by its wheels rather than hanging from the top tube. I have many different styles of bikes, straight, sloaping and no top tubes and can mix and match easily with this style of rack. The disadvantage is that the rack is a bit heavier and can be a handfull when mounting and dismounting from the vehicle.
If you prefer the type of rack that hangs the bikes from the top tube then think about the usefulness of a "stabilizer bar". This is a bar that extends from the rack below the bikes. You can put bungee cords down there that keep the bikes from swinging back and forth and banging into each other.
Remember, to use a 4 bike rack, your going to neeed a 2" receiver and a pretty substantial hitch. My own experience ends at 2 bike racks.
Thule makes excellent racks but you might want to take a long look at Hollywood Racks for very good products at good prices. I have used several of them with excellent results including withstanding a substantial rear end collision that scratched my car and gutted the grill, radiator and hood supporting structure of the car that hit me. (That was a Hollywood Boomer.)
Hollywoodracks.com (trust me, the website name sounds dangerous but isn't)[/Q
Do you have a link to this "stabilizer bar"? Which racks have them?