The heating element is to hot (need to do something to fix that) After 10-15 mins I had to pull over and unplug it.
I bet a Heat-Troller like the one Dual-Star sells for their heated grips would do the job!
http://www.dual-star.com/index2/Rider/heated_grip_kit.htm - scroll down below the grip heaters to see their Heat-Troller.