The official Calvin schedule has been updated to include tournament matchups, and while I was mostly right when I posted the list, I got the pairings for the Elmhurst Tournament wrong. According to the Calvin page (and the Elmhurst page), the opening round will see Calvin vs. Benedictine (6:30 EST), and DePauw at Elmhurst (9:00 EST).
DePauw is still reporting the matchups incorrectly (boo on them).
So what does this mean? It means that Calvin still has 17 guaranteed in-region games, whoever they play in the tournament's second day will be in-region, but it does reduce the number of possible regional games from the 21 that I reported earlier to 20. The big bummer is that Benedictine is officially (for the NCAA's purposes) 205 miles from Calvin (and they're not in the same defined region or administrative region), so the game cannot count a in-region.
