Watch the Drop 2, 3 Voicings: online guitar lesson by Brad Carlton from Guitar Lab: The Golden Arp
This lesson covers a very useful Add 9 form: the drop 2, 3 in 2nd inversion. There are two basic layouts for this chord (the video shows an alternate fingering for the higher voiced form). No real technical problems exist with this chord other than maintaining an upright posture with your fingers. This chord is derived from the 1st inversion close voiced add 9 chord. Follow the video for an explanation of the voice manipulation. I'll show an example of moving this chord over a pedal tone in the bass.