[Latitude 28]

Adam,
Of the four slide locks the seal was blown out on three of them to the point I could not see a failure point.  The last one had not started to leak so being very careful taking it apart I found this seal inside the lock in this condition. 
   

Finding this condition makes a solid case to use the Double X profile o-ring as stated in my post.  As a side note; they have preformed flawless on our slide locks.