TAZ Fan Dual Duct with smaller fan screw holes

The original design has big holes for mounting the screw inserts in the fan duct that was shipped with the printer. Pulling those inserts from the original fan duct and inserting them in the new piece is a pain. I modified the design to shrink the holes so that the screws can be inserted directly into the duct, self-tapping. OpenSCAD code is included.