I have created two custom post types, each with it's own slug. Each custom post type contains some articles with the same title. So ideally I would have . . customposttype1/mainarticle/ ...
I made a custom post type called "friends". I am able to correctly list my friends using this urls: http://mysite/friends/friend1/ http://mysite/friends/friend2/ http://mysite/friends/friend3/ ...