Get rid of standard bulky RepRapPro X-Carriage and nozzle mounts which you probably never upgrade to 3 color version. This is X-Carriage for single E3D v6 hotend nozzle mount and single standard RepRapPro nozzle mount at the back side for original RepRapPro hotend for back up if something goes wrong with E3D hotend or to mount additional cooling fan at this side.