I wanted to print the 120mm Fan upgrade from der0815typ ( https://www.thingiverse.com/thing:1501856 ) but for me it didnt fit as expected so i had to remix it.
Now you dont need any support, you can easy swap out the old bottom plate.
Things you will need:
4 M5 Screws
2 M5 Hexnut
1 120mm 12V Fan
4 Fan Screws
1 L7812CV TO-220
1 TO-220 Chiller
1 m of dual Cabel 0.4m²
Use some kind of food stands for your printer when the fan is to big to fit. I always use : https://www.thingiverse.com/thing:1424857
Conect your L7812CV with the main Powersupply (24V) and with your Fan. If you dont know how to use this kind of part than ask somebody who knows electronics!
Screw your Fan to the outside of the Fan Holder and fix the holder with the 4 M5 Screws. Normaly you can use the old Holes in your printer. It could be that you have to drill new ones because CTC is always upgrading their Printer chassis.