SPDIF mirroring was not included in the release of Pro Tools LE 5.3.2.It is possible to mirror tracks on the SPDIF output by holding down the control key (mac) or the start key (win) when creating a track output assignment. You will notice a "+" in the track's output selector after assigning multiple routings. You can control the output level by creating an additional master fader for the SPDIF output.