late additions again

I like the idea of late additions to keep the color of my beer lighter.

BeerSmith shows a significant increase in IBUS when doing late additions.

So I have a few questions.
Have others actually seen this increase of IBUs in the real world?

If it increases the IBUS by 20% can I reduce my boil time by 20%?

I have seen the suggestion of reducing hops by 20% but I would rather shorten my brew day than save hops.

You can shorten boil times with extract/steeping grains.

60 minute boils serve 2 purposes; 1) maximize hop utilization, and 2) Boil off DMS (extract doesn't have this problem).

Often when I get a new hop I do a 3 gallon extract batch, and boil for only 30 minutes. I make hop additions at 25, 20, 25, 10, 5 and 0. This is called hop bursting, and all the bittering comes from the finishing hops. It does require more hops, but results in lots of flavor and aroma.

The IBUs change with the calculator (as it takes wort gravity into part of the calculation), but they don't really change in real life all that much at all, all other things being equal.

I will keep doing the late additions then, well until I finish my BIAB set up that is.

I still think BS2 factors IBU's a little too much on the heavy side. They don't taste as bittered as it claims they are. But hop freshness,intensity of boil & all that play a roll as well. I think maybe tweaking the equipment & process sections may fix at least some of this. Gotta figure more of it out though. But BS2 has otherwise been saving a lot of experimentation in tweaking recipes or writing new ones. Late additions with my normal hop amounts & the like have been working out pretty good thus far. I can't wait to taste my Maori IPA with fresher hops around the end of next month. I also changed 3.2oz of chocolate malt to 8oz of melanoiden malt in my IPA recipes. Should get better color & flavor against the hops this time around.

Do the same recipe, one late, one full boil, same yeast, ferment and take detailed notes and report back. Tell us if you blind taste yourself which has higher IBU IF EITHER.

I started the experiment as described but failed. I did just as you said and save 6 bottles from the first batch to test along side the second
My refrigerator thermostat broke and froze all of them

I will have to try again.