From looking at the GIF on their site it looks like the rubber replaces the exact space that the rubber bump stop does. That said, you are not going to limit the little travel you already had, but in fact increase it during the rubber compression.

knaffie... if you have a moment... flex out your X to where the tire is stuffed all the way, the rubber should be fully compressed. There is probably some rubbage happening in the rear wheel well. Also, what size tires are you running?

There has to be a reason that the factory designed that size of bump stop. With my 33s I know that under full flex I am rubbing in the wheel well... using this rubber spring may increase that rubbage and possible cause more damage than its worth.