If you tape the corners up and have the box wrapped, there's no way someone could "peek" into the box without it being tampered with.
CP is not allowed and won't ask you what's in the box, as there is no customs within country. That being said, don't have it displayed that you're shipping a gun in a box, because that's just stupid.
Oh and +1 for newspaper, I always use that shit. Why would I spend 6$ on a roll of brown paper when I can get newspaper for free?
I change primaries like other people change socks.