You could try a crampbuster - this will allow you to hold the throttle with your palm on top of the throttle once you're going. Also helpful is some sort of throttle lock where you can take your hand off the throttle on flat roads to stretch and give your hand a short break. Go Cruise works well, is easy to engage/disengage and is reasonably priced.
Another issue might be grip size/glove thickness. Maybe too fat or too skinny for your taste? Do you have vibration in the bars or non-stock bar ends? Just throwing out some random ideas.
Mac beat me to it!
2014 V-Strom 1000 - Desert Khaki
2011 Burgman 400
2007 Honda Helix
2013 V-Strom 650 - sold