I know it has been a couple of months since this post, but being as I wanted to add this as well I went ahead and found a way to do it. I have not tested this with anything other then Invulnerability Fields as that is all I use. If it does not work for your specific hardener, you will need to find the GroupID for it and then add a duplicate section to the file under the switch ${GroupID} section. case 77 is for the invulnerability field, just copy it.
To install this, just copy the attached file into the core folder, make sure you back up the existing one.
