So I was thinking about installing a side fan on my Antec Gx500 and was planning to get a 120mm dust filter to go with it. But today as I tried to install without one, I found that none of my screws could work because the insides of the fans screw holes and the inside of the mounting holes on the side panel were smooth. I tried two fans, one of the fans that came with the case, and a cooler master fan. Looking for any advice for this. Thanks.