401(a)(26) and Frozen Cash Balance Plan

Cash Balance Plan freezes all contribution credits and new entrants into the Plan. The Plan is top-heavy. The Plan is covered by the PBGC.

The question I have is when it it considered underfunded for the exception to 401(a)(26) to apply?

Does the AFTAP have to be less then 100%?

If the AFTAP is greater than 100% but assets are less than the sum of the notional accounts is that sufficient to be considered underfunded?

If the assets are less than what is required for the Plan to complete a Standard Termination under the PBGC rules is that sufficient?

To throw out some hypothetical numbers assume

Plan Funding Target (@95% corridor of ARP stabilized rates) $510K

Plan Funding Target (@105%corridor of ARP stabilized rates) $490K

Plan Assets (MV @ valuation date) $500K

Sum of Participant Account Balances $530K

PVAB for PBGC Premiums $600K