Mash Profiles & Hop Addition IBU Changes

Over in the All Grain & Partial Mash Brewing forum, there is a thread, "Trying to get more "body" in my beers... Techniques?" that got me to thinking about Beersmith. The thread is Here: https://www.homebrewtalk.com/f36/trying-get-more-body-my-beers-techniques-95100/

I am a Beersmith user and have various Mash Profiles set up. If I choose one for lets say a, Light Bodied" beer and then change that recipes mash profile to a, "Full Bodied" beer, will the IBU's of my hop addition change?

Great question. I actually was thinking the same thing. I have Beer Tools and it has options for several different types of hop utilization (mostly named after the guys who worked out the formulas), I'd be curious to know if any one of them take body (I.E. Mash Temp) into account and which one is most commonly used.

I'm not a beersmith user, but my understanding is that the mash profiles affect the fermentability of the wort, but have very little (if any) impact on the original gravity.
Anything that happens after the boil will not affect the IBU's, but it is possible that the gravity of the wort during the boil could affect them (although this is subject to some debate).
The most commonly used methods for guesstimating IBU's are Garetz, Rager, and Tinseth. There are others that I have not yet researched.
Norm Pyle's Hops FAQ gives some information on the various methods, but I have no idea how accurate this information is.
FWIW, I use Tinseth, because Promash supports it, and it usually falls between the other two.
Whatever method you use, they only provide estimates, and the real values will vary according to the equipment and procedures that you use.

-a.