Ultimaker bottom fan replacement

The default fan that comes with the Ultimaker 3D printer to cool the electronics mounted on the bottom is very loud. It makes a grinding noise. Atleast, for a lot of us it does. The fan is probably not ment to be up side or down or something. Anyway. It is so loud you probably want to replace it by something else. I used two 60mm fans to replace it with some very simple mounts. I have seen replacements as large as the original wooden plate. I like to use the fans to bridge space from M3 screw ho