Since the entire airplane yaws pitches and rolls at exactly the same rate there is absolutely no performance improvement by being close to the CG. That of course assumes the fuselage, wing, etc are reasonably ridged and not flexing significantly with control inputs.. That's unlikely but if it were the case there is still no guarantee that being near the CG would be the best location and in fact nearer to the source of the flex would probably be the best..The most important thing is that it be mounted square to each axis and that the orientation is set correctly so it knows which axis is yaw, which is pitch, which is roll and which way is forward so it knows how to apply corrections..Most use the default orientation but it can be changed in the software to match the installation if you need to install it sideways or inverted for example..