Cooling duct to replace the original that melted on me.
The screw holes are hexagonal. You can use the screws from the duct to form thread into them. My strat is to start digging it in one or two turns, then wiggle back and forth until you feel the plastic softening up from the friction. Two wiggles per proper crank, and you should end up with perfect round threads.
Maybe loosen the fan screws inside the shroud if the fit is too tight.
The author marked this model as their own original creation.