http://cj-motorsports.com/pdf/370z%20S1%20Install.pdf
Scroll down to page 10.
You need the first flange to be completely inside the adapter, trapped in by the lock collar. This is how the fitting cannot just be pulled right back off at any time. If the lock collar isnt behind the first flange (between the 2), the fitting will literally just slide right back off the pipe as easy as it slid on.