I think he has no clue, I would explain it to him in the least complicated way possible and if he is willing to still paypal you the money I just wait till the money clears into my bank account before I ship anything. Tell him he would have to wait till the money clears into your account before you ship, and that is just how you do it to protect yourself and see what he says. I guess if this is a scam I don't see the angle.
no way.. if it were me, i'd walk away. he could always do a charge back!