The filter capacitor can be installed at 3 locations in general.

#A. The capacitor is soldered at a power plug / the connector of battery & ESC .

#B. The capacitor is soldered directly on the ESC or at a position very close to the ESC "with very short pins".

#C. The capacitor is soldered at a position close to the ESC but the capacitor module has long external wires. (This method is similar to the usage of the cap module of many high-performance ESCs for a four-wheel application. ex. XR10 Pro ESC.  Although it is not the ideal situation to protect the ESC, the overall volume of the ESC would increase dramatically that it may be a problem for some chassis. therefore #C location is alternative method use in practice. 

According to our factory testing, neither #A nor #C has a good effect for filtering the ripple-current effect. Specifically, if the battery is more than 2S, the filtering effect of #A or #C method is bad that a capacitor does not serve its potential value. In contrast, #B location works fine under all conditions we have tested. This conclusion can be easily proved by monitoring the ripple waveform from the oscilloscope.