Adjust Projected/Accrued Benefits

We have an overfunded DB the client needs to terminate.

There is plenty of room to raise projected and accrued.

There are 4-5 vested terms that terminated more than 5 years ago.

Question, although possible to recalculate on a new benefit (obviously to reduce the overfunding), since they terminated over 5 years ago and have NOT been paid out anything, is it necessary to recalculate these benefits???

It's a reasonable question.  I believe the answer is Yes.  You should read the IRC 4980 statute here:

https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title26-section4980&num=0&edition=prelim