Good discussion here: http://pistol-forum.com/showthread.php?9787-Dark-Star-Gear-AIWB-(Casual-Carry)

A distinction I would like to make is that the clip-on/casual carry holster is a straight drop IWB. I hate the trend of calling a foldover/taco holster that is vertical an AIWB holster. This particular holster happens to work for most people in the appendix position but differs from my AIWB with a built up wedge.

The clip doesn’t quite work well with my wedge, yet. With the wedge comes more rollover, or the feeling of, which is why I extend the small auto AIWB’s to approximately G19 length. The straight drop clip-on holster does however work quite well in the appendix position. Keeping the holster thin and using a secure attachment avoids the need for extra length to prevent the rollover. With all things it is a compromise and if something doesn’t work just speak up and I’ll do my best to get ya squared away.