I bought a Swagman that holds 4 bikes. It holds the tires and also has an upside down "U" hook that slides down over the top of each bikes top tube to keep them from moving around. Its a very secure hold and doesnt allow the bikes to touch each other. It cost me $280. I can load 4 bikes in 45 seconds if I speed through it, and they dont move not 1 mm when Im done.
Heres a link to it
http://www.swagmanbikeracks.com/64665.html#
P.S. Looks like I got ripped good at the LBS I bought it at by $90. Im going the net route from now on.