Have not done the MB-Tex, only leather on dash, but I can say with the leather, you glue directly on the MB-Tex dash pieces. Originally, the factory just used the MB-Tex pieces and re-covered with leather, if leather was ordered. Now to answer your question, I would think you would do the same, because under the original MB-TEX was a thin padding of foam rubber. You would not want to disturb the foam rubber padding by tearing off the MB-TEX.
Bob