This is not something that is required, however, with the high grip tracks in the UK, this may be something you might find useful if running on carpet or astro.
I have removed 3mm from the rear side of the rear arms. It increases the available wheelbase from 275-278 up to 275-281. As a point of reference, the Xray XB4 is 279-281, so you can see how much adjustability this gives you for different surfaces.
Pictures below, any questions just ask