You may get away with one fan, but the 1512 1.5d is a very power hungry motor and is very demanding on your ESC and batteries.

I race my rc8 which tends to be harder on the ESC/motor than just bashing/street runs, so two fans is a little extra insurance. My temps dropped about 10-20 degrees from the second fan on the bottom of the ESC. I have never thermaled my Mamba.

It isn't hacking up anything. Just cut an equally sized hole in the bottom of the case for the fan and screw the fan on. Takes all of five minutes to install.

I've been there, done that, and got the t-shirt. Just trying to save you a future headache.