I just finished my install. I pressed it in all the way around. Tried to slide it but didn't think it was going to slide through the corners.
My method was to use a flathead screwdriver. If you press the rubber in with the screwdriver at an angle that is around 45 degrees to the slot. It goes right in without too much trouble. I started pressing it in at an angle closer to perpendicular with the slot but that was actually not the best angle of attack.
Still not the most fun
Don
