I just went through this yesterday. My card (SuperMac ColorCard SE/30) has IC pins sticking out all through the section where it might touch the chassis. The card has mounting holes that are sort-of near those two holes in the chassis, but offset about 1cm away. Strange! My solution was to tape a thin strip of cardboard on the inside of the chassis, so if the card wobbles in the PDS connector it will touch the cardboard instead of the chassis. It's not very professional but it does the job.