Question on hop extraction for my next beer

[J2W2]

Hi,

I'm brewing a 5.5 gallon batch of oatmeal stout tomorrow, and I'm going to try a late addition (just after flame-out) of the dark steep grains to see if it has an impact on bitterness.

I'll be using a gallon of water for the steep, and reserving another half-gallon to rinse the grain bag. This means that my 60-minute boil will start with 5 gallons of water instead of the full 6.5 gallons.

Based on the numbers in BeerSmith, it looks like the reduced volume will drop my IBUs by just over 25%. To compensate, I'm thinking of increasing my hops amount by 25%. BeerSmith says that will give me the IBUs I'm after.

Has anyone else done something similar, and does this hops increase make sense?

Thanks for your help!

 

[ncbrewer]

I just did that a short time ago - increased the boil gravity. I used the Tinseth formula to check hop utilization and IBUs, and increased hops accordingly. The beer came out just like I wanted.