I designed this to accommodate larger fans. I am using a 40x40x20mm part cooling fan and a 30x30x15mm hot end cooling fan. It mounts to tapped holes in the bottom of the extruder with three M3 screws. I used extra 6mm button head ones that came in my kit. To attach the fans, I used some craft wire and twisted the ends. you can also drill out the holes and use nuts and bolts if you want. I can now print beautiful 20 degree overhangs. 15 degree overhangs don't look too bad either. The ribbing prevents rotating air from coming out of the nozzle at and angle ducting to the hot end heat sink optimizes the air coming from the fan. An increased airflow fan here doesn't really make any difference. I am working on a wrap around duct to cool the part evenly but space is tight.