then why would the Post-1990 complain about not playing in Carolina enough? I ask because 1 spot could rotate among the 4 NC schools and the other spot could rotate between the other 3 schools. In VT's case 1 spot would go to UVA and the other spot rotate among the 6 schools.

If anything, I would the Pre-1990 teams would complain about not playing a FL team enough because they wouldn't see playing in GA and SC as a fair trade. Given that the ACC right now has 5 "football" schools, I could see some of the Post-1990 schools complain that the division has 4 of the 5 schools.

A reason the ACC may want to go with the zipper model and continue using 1 protected cross-division game with 7 natural pairings (which means VT and UVA in opposite divisions) is because it may make it easier to convince everyone to switch to 9 conference games. Teams would have 1 protected cross-division game against their "main" rival and the remaining 2 games rotate among the remaining 6 teams. Basically it would mean the 6 teams are divided up into 3 pairs to make it easier for establishing future rotation schedules. Also, it would mean both divisions have equal access to the same state or region.