Affect of Section 436 on Lump Sum Termination Distributions from an Underfunded Plan

[Guest Dressageho]

I have a client who has an underfunded Cash Balance Pension Plan (AFTAP is just under 70%). The Plan was terminated and the majority owner signed an election to forego benefits for PBGC purposes. The question is whether this will carry over for IRS purposes to allow the Plan to be considered 100% funded. We've not had a problem in the past because the terminating Plans have always been at lease 80% funded and not subject to limitations on how benefits are paid out (i.e., lump sum distributions of the entire benefit). I know the final Regulations have just been issued under 436, but I could not find anything particularly useful and wondered if anyone had any ideas, suggestions, or citations (or links) they wouldn't mind sharing.