Hop utilization from whirlpool additons using BeerSmith, what about late hops?

I'm planning a pale ale/IPA and was looking at removing the 60min addition and instead go for late additions and a big whirlpool addition, target is 40 IBUs.

I have a 3-vessel system where the mash tun also act as whirlpool after the boil. All vessels are 70l (~20 gal) and I usually boil 60-65L (~17 gal). The mash tun/whirlpool is well insulated and I have been able to keep temperatures above 90C (195F) for more than 20min, which should give me a decent conversion in the whirlpool.

Now to the question, should I calculate an IBU contribution from the other late hop additions? I don't think BeerSmith takes late additions into account when doing a whirlpool IBU calculations.
My thinking is that if I add hops at 1 min before end of boil, transfer wort (including hops) to the whirlpool, the 1 min addition will add IBU's in the Whirlpool as well. If I add 33 grams at 1 min, BeerSmith calculate less than 1 IBU addition, 33 grams for a 30 min whirlpool give ~15 IBU. Is it correct to think that these two additions should give 15 IBU each meaning a total of 30 IBUs?

Of topic, whirlpool with or without lid?

If you go the Professional Brewers section of this form and type "Hop Utilization from whirlpool" into the search box, you will find some info there.

As a home brewer, I have been working on my IPA process for a few years now. You are looking to put a exact number on the whirlpool bittering process. It is an aroma & flavor process primarily with the bonus of adding SOME bitterness. You don't need to worry about an exact SOME because it is something that works out to be a best guess. Your palate will tell you what is too much. I let BrewSmith give me the best guess. Your whirlpool equip will give you more bittering since it holds the temperature up. Mine cools faster and it is effected by whirlpool velocity. I just go visual on a slow whirlpool speed, because hops do effect my pump flow meter. I whirlpool in the boil kettle. Transferring boiling liquids is dangerous. Pros do run off into whirlpool vessels and I will leave that process to them.

I wouldn't whirlpool a pale ale @ 40 IBU. I have used whirlpooled only additions but have gone back to 60 min, 20 min, and whirlpool additions because the beers taste better. I bitter a lot with Magnum @ 60 min. since it doesn't dominate the late and whirlpool additions with a competing flavor. For a 75 IBU IPA, go with under 30 IBU 60 min. Over 75 IBU bombs, I go with under 40 IBU @ 60 min. Magnum doesn't work well if you want to go dank.

One-two minute additions are done by professionals to hydrate and get the hops down in the wort before whirlpooling. It is nothing to worry about in home brewing. I like my whirlpool additions to be floating while I get my pump going.

Water is key to a great refreshing IPA. My target is a 4:1 ratio of SO4/Cl
With a finish water profile of Ca 106, Mg 27, Na 1, SO4 192, Cl 48

When you whirlpool you use the lid. Sanitize your metal lid by letting the boil steam do the work by adding the lid slightly agar during the last couple minutes of the boil. A lot of water condenses off the lid during the whirlpool process.

IPA will whirlpool  for 45-60 min. Then allow to settle for 20 min. That's up to 80 minutes where some level of isomerization will occur. However you calculate your IBU's be consistent and combine that with your palate. You can get better guessing IBU by drinking craft beers with a known IBU value. Just be consistent with your process.