If you have to choose a good configuration for rear motor, it is that one :
Speedo/Shorty battery/Reicever/Servo on line...( I haven't got photos of mine...winter period...Mid motor rules
)
Rear motor is the king on slippery tracks...with the shorty battery centered.
It depend on which battery you are using...but the Bmax2 works well "light" with shorty battery.