As far as i know, automatic bids fork as follows

1. each bona fide league (league has been approved as a league in the
sport by the NC2A, has the requisite number of members or has been
granted an exception as CHA was when it dropped to 5, and has
satisfied any probationary period proscribed by the NC2A) is entitled
to an automatic bid

2. the league gets to decide, i believe subject to NC2A ratification,
which team gets the autobid.  Normally, the choices have been for
leagues to select the regular season champion or the league tournament
champion as the benefactors. Most leagues use the latter.

some things i've noted in other sports and other divisions:

1. six is not enough, and 8 is probably enough
2. even sizes are better than odd sizes
3. balanced schedules (if you like that sort of thing) don't work for
   league sizes bigger than about 10
4. travel to all sites is not created equal
   a) alaska is time consuming
   b) schools not located particularly near major airports will normally
      either have to change planes or take extended bus rides. The
      ones that come to mind are huntsville, the upper peninsula
      teams, bemidji, and north dakota
   c) it is always entertaining to use trip routing software to see
      how long a bus ride will be, and if the distance is over the
      NC2A threshhold for air travel.
      omaha to colorado springs about 9 hours
      omaha to south bend about 8 hours (548 miles)
      no, i'm not picking on omaha. when my daughter lived there, i'd
      make the drive regularly. (i know, i know)
5. comparing relative team performance across leagues is, at best, a
   nightmare 

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