Stereo Guitar Technique

Although I use this specifically with RealGuitar (MusicLab), it would work with other stereo sources, like actual stereo output guitars instead of VSTs.
 
It is easy enough to have acoustic 1 on one side of the stereo field and acoustic 2 on the other, and it's even more effective when they are playing the chords in different inversions (one open and one up the neck).  But try this:
 
1. Use stereo guitar for both instances (panned to the middle of a stereo track since the sound is spread across the stereo field).
2. Play the two guitars in different inversions.
3. Now insert Channel Tools in one of the tracks (for example, the high inversion) and reverse left and right.
4. If you use the Time feature in Inspector to shift one guitar's MIDI back a few ticks and the other one forward a few ticks, the sound gets even larger.  (With RealGuitar you will need to shift both the notes and strumming patterns/keyswitches the same amount, which is easy if you put them in the same MIDI track.  I put them in separate tracks to simplify editing.)
 
This way the high and low strings of the guitars will be on different sides of the stereo image and they will be playing different notes.  It sounds like more than 12-strings.
 
With RealGuitar, might want to HPF at 100-125 hz, dip a little around 800 hz, and maybe shelf-boost a little around 10K hz—but of course your specific guitar sound and your ears may lead you to different settings.