restructuring and reasonable classification

[AndyH]

DB plan provide safe harbor formula of X per year of service is later amended to provide that employees hired after date G instead get a lower benefit, still a safe harbor. Each group has been tested under the ratio/percentage test and determined to pass, so since each passes 410(b) and is a safe harbor, the plan as a whole qualifies for safe harbor treatment.

Now the ratio/percentage test does not pass. Can the Average Benefits Test be used to restructure? IMHO the question comes down to whether someone is hired befor or after date G is a reasonable classification within the context of the NCT requirement of the ABT. Opinions?