Hey, sorry to revive a super old thread for a shamelessly plug, but I'm currently launching a product which clips right onto the Grip, and you twist it to actuate your thumb throttle. It's super easy to take off, or rotate out of the way, so you can just use it part time.. like for that long ride back. I'm glad to answer any questions. Check out dualthrottle.com
and pledge on Kickstarter if you want to back the project, I'd appreciate the support.
I have it on my 550sx and it works great.