I added a filament guide, based on my tension nut, so I don't need to worry about the filament looping off the roll on a long unattended print job. The tension nut is tight enough that it doesn't need a screw to hold it in place.The hole has a large rounding fillet on both sides so the filament will pass through easily and the arm should accommodate various spools. You can add a small square of foam in front of it and push the filament through. The foam will clean off any loose dust or particles on the filament before it gets to your extruder.  If you are using PLA, try a drop or two of pure canola oil on the foam.  Seems to work wonders in keeping PLA feeding smoothly through your extruder, both in my experience and according to comments from others.