Re: String Stops
Weather you use glue or another adhesive product something is necessary to insure the cable stops remain fully seated as tightly as possible to the bumper rods.
If the cable stops should loosen and move up even a 1/4" off the base of the bumper rods, you will quickly develop a split in the rubber bumper. You will also likely have uneven pressure being applied to your arrows during the launch cycle because one side of the cable comes to an abrupt stop slightly before the opposite side. This is why both cable stop bumpers should be firmly seated in their lowest position on the rods.
You may not think it's that critical, but for a crossbow that you are trying to achieve under 3" arrow groups at 80 - 100 yards everything is critical.
Yes, I think the front bumpers are made of the same material as the rear ones.