This article has a bunch of fun trivia about the various seed/matchups.  Of interest to us:

6 vs. 11
No seed matchup has been turned on its head like this one.

From 1985 to 2009, No. 6 seeds won 69 percent of the meetings, but in the past nine years, they have won just 44 percent. It has been decidedly worse for 6-seeds in the past three years, as they have lost eight of the 12 matchups.

The tide may have turned between these seeds, but one thing that has remained unlikely is a sweep. It has been 15 years since the No. 6 seeds swept all four meetings, and this year marks the 30th anniversary of the only time No. 11 seeds won all four meetings.

So the good news is I won't look crazy for turning in a 6 vs 11 upset in my office pool.  But even better news is the following:

Proof that 11 is the new 12

One of the more interesting trends in the past handful of years has been the annual presence of an 11-seed in the Sweet 16. As bracket numerologists can surely attest, this discussion used to be about the No. 12 seeds, but no longer (more on that in a moment).

At least one No. 11 seed has reached the Sweet 16 in each of the past five tournaments, its longest such streak. By comparison, zero No. 12 seeds have made the Sweet 16 in the same span.

Looking at the past four years, No. 11s have won an impressive 18 games (and that's not counting the First Four games), while 12-seeds have just three wins. Only 15- and 16-seeds have fewer in that span.

This isn't just coincidence, though. Blame it on the expansion of the field to 68 teams, along with the addition of another higher-major automatic bid when the American Athletic Conference was formed.