What are the standards the IRS is to use in approving a change of funding method? In the case at hand, a DB plan is changing to funding method that would be automatically approved under 2000-40 but for a prior change was made in 2000.

I believe they are going to want to know your justification for changing method, especially since a change was recently made to the current method. They will also probably want to know the impact on funding. Assuming you are reducing your contributions, it may not be easy to get this approved.