I agree that the Chappy is not a true back tension but it can be shot as if it were.The trigger must be set to fit in the palm of your hand as you start using your back muscles the release will go off.Hard to describe but it can be done.
The Chappy is most likely not the choice if target panic is a problem.Most that I know that suffer from target panic and that use the Chappy have more problems with panic when using it.
I use the Chappy and love it but it isn' t for everyone.
I would suggest the Stanski release.ST-1, 2, or 3 depending on your hand size.It is a back tension that will not go off premature and requires no set triggers to make that possible.
it is available at
www.specialtyarch.com