Watch the Two - One - One Forms online guitar lesson by Brad Carlton from Guitar Lab: The Golden Arp
The 2-1-1 form of the add 9 arpeggio in 2nd inversion is interesting because the 5 can be sustained as the lowest voice. This can create a big sound since the bass will probably be playing the root. One technical issue can be the 4th finger roll that occurs on the three lower forms. This can be remedied by using the 3rd and 4th fingers instead of the 4th finger alone. When you play this inversion on the top three strings, you can apply a one finger-per-note approach to fingering. Combine these 2nd inversion forms with the root position and 1st inversion forms you learned in the previous two lessons to help your string axis visualization of information on the fingerboard.