I'm building an earth pentacle to use in my rituals, but i have some doubts on its creation.

I'm building it around 6 inches, out of some wood boards i glued together.

I read in "Modern Magick" by "Kraig" that it is better to be concave, because this would direct the energy directly back to the one who sent it, in case of an attack.

I really don't agree to that, as i don't see how anything reflects back to its origin on something concave differently from something flat. I also don't understand why it has to be used against attacks, as it is obviously meant as a defensive weapon, or a shield. And a shield is definitely not concave, more the opposite.
It just doesn't add up, Kraig's theory, and it leaves me confused...

Could anyone give me some advise on this.
Also, the origin of the god names that are meant to go around it are not given in Kraig's book, I would like to know them to. (IMG:style_emoticons/default/huh.gif)