I have had very good results with Hollywood racks. After the bike is mounted, a bungee cord of the appropriate length (by the assortment kit at Sears) from front wheel to stabilizet bar and from rear wheel to stabilizer bar pulls down on the bikes and pretty much confines the sway.

For a few years I used the Hollywood Boomer (single boom rack not dual like the roadrunner). Since I carry a wide variety of bikes, problems with things like no top tube, severely sloping top tube, suspension components in the way and handlebars interfering with adjacent bars, saddles etc have caused me to bite the bullet and change over to the style of rack that holds the wheels in a tray. The Hollywood sport rider is my current choice. There does not appear to be a weight specified, but I suspect that it does not weigh anything like 100lbs. This rack is convenient because of the variable wheel base settings and the ability to offset bikes from side to side to avoid interference.