I used a hack saw to shorten the throttle tube to fit the BMW grips. (make sure you smooth the cut on the throttle tube by filing/sanding and remove any debris to keep the throttle from dragging) I then measured, center punched, and drilled new holes in the handlebar for new locator pin positions for the controls. This allowed me to slide the controls outboard to take up the extra space from using shorter grips. Some folks grind down the locator pins but I preferred to keep them and drill new holes. You will also have to drill a new locator pin hole in the left side handlebar.
I later installed a G2 throttle tube and shortened it the same way. Everything looks original and works fine with a Throttlemeister.