Just posting research I've done on these pairings. Feel free to add your own + thoughts on this year's match-ups.
#5 NOTRE DAME [-6.5] vs. #12 GEORGE MASON
#5 MICHIGAN STATE [-6.5] vs. #12 TEMPLE
#5 CLEMSON [-6.5] vs. #12 VILLANOVA
#5 DRAKE [-4] vs. #12 W.KENTUCKY
SINCE 1990 [72 games]
12s have won STRAIGHT UP 25 times.
12s have lost by 10 POINTS OR LESS 24 times.
12s have lost by 10 POINTS OR MORE 23 times [3 by 10 exactly]
Only 5 tourneys have featured 2 or more #5 seeds winning by double digits.