George, you had me at "CLEAN".
here's what I do to most of mine because I don't like wires , they use the same size hole so you can switch to each style any time.
http://www.oldminibikes.com/forum/project-logs/6090-going-kill.html
They work great and are like a "panic button" that is right where your hand naturally hangs (on most bikes anyway). Also if you where to be laid down with engine running you could be in a position where you can't reach the bars,, where the engine is in the middle of the bike and you just slap the top of the engine.
I do have two bikes that someone mounted a kill by the grips and they aren't much faster and look like ass. (to me anyway) I like less is more,,clean ,clean, clean. Some people get carried away with adding all kinds of mods to their mini's and they no longer are mini's! "KISS" >>>> "keep it simple stupid",,, less is more,,,,oldschoolmini's!
I guess on the bars would be good for kids thats if they remember anything under stress. :thumbsup: