From a law enforcement perspective these were popular in the mid 90's for about five minutes. There is no retention technique that can be used. Concealment also seems problematic as when a cover garment rides up or works in between the grip and body who is going to tell you about it as you can not see it yourself. They seem to print terribly when you bend over. When you draw as a right handed person, the muzzle is pointing to your left behind your back, not at the threat. If you are grabbed at that point with you arm behind your back, your are at a great disadvantage. Drawing while actively fighting, not going to be easy.

Just some points to ponder.

If your comfortable with these, great. They are not for me and yes, I did have one for a very short time about twenty years ago