not gonna be real hard for him to find on his own staring in the window
I don't think that is a good place. It is concealed for purposes of the law, but visible for all to see, including the pickup next to you at the stoplight.
My plan, if I get stopped, is to hand the extra piece of paper to him, say "I also have a permit to show you", and after he digests it, ask "what you like me to do?" I am not required to do so, and it would depend on why I was stopped, I suppose.