// once. (2nd extruder x offset and temp offset are set using: M605 S2 [Xnnn] [Rmmm])
// Mode 3 (DXC_SYMMETRIC_DUPLICATION_MODE) : Symmetric Duplication mode. The firmware will perform similarly to DXC_DUPLICATION_MODE except in a mirror
// image of the first x-carriage. ie. If you are printing a right hand shoe on the 1st extruder, you will
// get a left hand shoe on the 2nd extruder.
// get a left hand shoe on the 2nd extruder.
// This is the default power-up mode which can be later using M605.