I neglected to mention the reason for using the same material as the door seal for the patch. As the door seal inflates it gets bigger. This causes stress in the adhesive between the seal and the patch. If the patch is a rigid material the stress will be concentrated along the perimeter of the patch. Put a piece of scotch tape on a balloon then inflate the balloon to see this effect. This stress concentration can lead to "peal".  Using a thin patch that is the same material as the seal reduces the stress concentration as the patch can now expand with the seal.

Regards
Brent Regan

<<<During construction a "helper" managed to stab my door seal with an Exacto knife. I fabricated a small round patch out of the rubber material  that was supplied in the kits as the mating surface for the seals. First I thinned the material on a belt sander to about a millimeter thick. I then punched out a round patch. I roughed the seal area with 220 grit to remove the release agent and scuff the surface. I then used RTV silicone to glue on the patch, holding it on with a piece of masking tape for ~24 hours. That was 16 years ago and the patch is still holding fine.>>>>