in 1997 I got a 24" Challenger. I had an idea that I needed gears on it so I put a 5 speed screw on block onto BMX hub, added some spacers under the cone nut and crammed it into the frame. I used a simple thumb shift with outer cable all the way to the mech, that was held on with a bolt on hanger. I also put a skateboard wheel on a hinged DC seat clamp above the chainring to help keep the chain on.
I rode it for a while but I soon found out that you really dont need gears on a 24" Cruiser (If you are cycling anywhere far enough to warrent Grears, you probably dont wanna be on a 24" Cruiser). On top of that, it took away the clean look of a race BMX, it clanked around loads when you jumped it, and the chain came off if you did a 180. I changed it back to single speed and was much happier with it. At the moment I am just getting some parts together to give it a rebuild.
When I still had gears on it, a mate was doing a street riding article for a MTB magazine and asked if I would ride my 24". I found the magazine today so fired up a few scans. It was Total Bike, from Oct 1998.