MGT1, it's also possible to make a 1G J4 courrier. Short the cargo for sensors, and it makes a decent fleet scout.
In MgT1 you can even build a J5 2G unmanned jump courrier drone (I guess that would be an enlarged jump torpedo). See Zhodani Drone Courrier (though, as explained in the thred, I latter thought it would be better fit for K'Kree, who would have problems in keeping manned small courriers).