Hey Tom,
There are a few things you can do to get it to run ok under your low profile B4 body.
The recommended method is to remove the fan from teh top of the ESC and mount it sideways next to the ESC so that it is still blowing air across the ESC.
Some people cut openings above the ESC to allow the fan to stick through the top but I'm not sure you like the idea of cutting up your body.