I have mounted more than a few sets of barkbusters over the years. I must be the last guy in the world to have figured this trick out. To modify the throttle tube I usually take the grip off and hacksaw the end off the plastic tube, then razor knife a reasonable hole in the grip. Tonight I used a 7/8" hole saw that just fit inside the throttle tube to drill a nice perfect sized hole through the end of the tube and the grip, as a unit from the inside. Slick. I am always amazed at how long a guy can stay dumb. Cam.