Hi Jamie.
I made this variable ratio quick turn throttle with the stock piece, plastic strapping and J&B Epoxy almost two (2) years ago, today. You can see from these two pics how it was constructed. What you can't see is small groove cut into the added plastic to center the cable action. There was also a bit of engineering (Dremel work) needed on the stock throttle housing. This single-pull throttle leads to a dual-pull Venhill junction. I run pre-mix, so no oil pump to control.
It works. The bike picks up nicely and progressively, cutting about 1/3 from the full stock action of the throttle. Mine is a track only 3xv. I'm not sure how this mod would hold up for a street bike, but its been solid on the track.
Cost: About $2 USD.
Thanks for your question.
Steve