TRY SHOVING THE POLE UP YOUR ASS TILL IT REALLY HURTS AND YOU HAVE DIFFICULTY ARTICULATING WORDS AND THEN JUMP OUT THE BACK OF A MOVING CAR.........
no but really..........eyeball the length you think you'll want, then heat up the grip slowly with a hairdryer to pull it off. Use a coping saw to cut the pole to length, use some masking tape around the cutline to make a clean cut without any burs, then slap the grip back on.
then go beat your dog or sister with the newly cut poles