create the mission and save it
then shut down the mission
open up the mission.sqm which you will find in your
user/username/mpmissions/missionname
find the entry for your ninja addon unit
and then simply edit the
side="XXXX";
to whichever side you want it for
and save the file
Problems may occur if u re edit the mission, sometimes the mission.sqm returns it to its original side.
Once you've finally saved it for the last time and pbo'd it, the problem wont re-occur