I have difficulty in this department, too. Several things that can hel:
1. Relax that grip. Most new riders try too hard.
2. Try slightly adjusting your wrist angle. This helped me immensenly, but feels strange at first.
3. Consider physical therapy. The wrist strengthening and stretching exercises they taught me helped me with the tingling on the bikes, too.
4. Consider installing a throttle lock or tensioner, such as the Throttlemeister, to allow relaxing the throttle hand periodically. Lots of good threads on this forum in that regard. Full cruise control possible, too, if you prefer.
5. Seriously consider handlebar risers or replacements. BRP has the 1" riser, which usually isn't enough (but we like ours). No Magic Neon has handlebar risers, Kewlmetal has replacement handlebars, and Heli-bars makes a barback/riser.
6. Change your seating position a bit. My wife is 5'2" and sits way forward. This would make me nuts, but works for her.
Hope you get things worked out.
-Scotty