Hey! Firstly I'd like to let you know I'm a volunteer, not a former developer of the plugin in question.
I don't see what the issue is here? If your saying that the armor isn't outlined, that's just how the glow effect works, it highlights the player/entity not the armor itself. This seems more like a Minecraft issue than a ItemsAdder issue if you just don't like how the glow effect works?
Let me know. thanks!