I got some work done on my air filters today. I've had previous experiences with them getting knocked off with any sort of handling. I thought about it and I've came up with a solution that works for me. All that is needed is a #77 drill bit, .015 brass wire, and your air filters. My wire is from Titchy, and my Filters are Details West. First look to see exactly where the filters are mounted on your prototype and mark it under the walkway. Next drill a #77 hole in each mark. My filters are DW-139. First trim the flash and smooth both tops of the filters. Next drill a #77 hole in the tops of both in the center of the larger filter. The smaller filter hole will be slightly off set towards the back (I forgot to take a picture of this step). Next I trimmed down the wire sticking out of the bottom of the walk way and glued the filters into place. All that is left is to run the air lines with .015 brass wire.