Re: Rubber insulators
That's not the way to install it correctly. The bolts will go through the holes and the holes will line up. Opening up the holes in the rubber will make for a loose, sloppy fit.
Do it right and you won't have problems. Take short cuts and you're letting yourself in for failure.
Many before you have installed the rear sprocket and most have had to do a little struggling to get it right. Follow our advice and you'll be okay.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"