Having a hard time with bittering

[Cromwell]

I use BeerSmith to help me calculate amounts of hops for bitterness according to style, but I want to try skipping the bittering (early) hop additions altogether in favor of more late additions. The problem is, BeerSmith says that you get 0 bitterness from hop additions at flameout, but I don't really think that's true. If I toss in an ounce of 7.9% Saaz at flameout, and then open the valve to drain the wort through a CFC, it'll be a good 10 minutes before the wort is entirely drained. (Gravity)
So how do I calculate the bitterness here? Do I add 10 minutes to the calculations for bitterness for each hop addition, so that something added at 5 acts like something added at 15?
Pretty sure if I added 1 LB of Citra at flameout, it wouldn't have zero IBUs.

 

[ReverseApacheMaster]

Back up the time. Beersmith assumes you are going to go straight to cooling. If it takes you ten minutes to cool, then your flameout addition should go into beersmith as a 10 minute addition.