I am just using a rubber o-ring between the flange of the throttle grip and the switch housing. Just enough friction to hold it, but not so much you can't easily rotate the throttle. Cheap and effective, very simple. You just have to remember to roll the throttle off.
Ooh, I don't like that idea so much. I could see a lot of reasons why that'd be a much greater risk than a cruise control you can turn on or off. Like in city driving.
My ride: 2010 T-Bird
SO's ride: 2009 Can-Am Spyder