No chill, slow chill = more IBU from late hop additions
No chill concerns for hops is late additions will continue to isomerize until below 175°F.
Removing the hops will help, but any alpha acids already released in the wort will continue to isomerize.
Some recent studies show that 175°F isn't like a switch, but temperature and time follow a curve for ...
No you won't notice a difference.
While alpha acids and precious volitiles fade with age and air exposure. You won't register any difference with the limited time you're talking about. I would wrap them in foil or use a zip lock, to prevent contamination that may not get sterilized (whirlpool additions), and at least refrigerate.
Photo from Coachella ...
Why not save the hops you don't use and use them in another brew? Although vacuum sealing them is the best way, they'll keep fine for several months in a zip lock freezer bag. Just squeeze out as much air as possible after you put the hops in the bag and keep the bag in the freezer. That way your current beer gets the proper amount of hops and you aren't ...
On a theoretical level, with worts that are completely free of suspended solids, then for the quantity of iso-alpha acids extracted would be the same. In practice, there are some limiting factors, that make scaling down (using relatively more hops in less solution) non-linear:
there is a maximum solubility of iso-alpha acids, around 120 ppm/80 IBU for a 5% ...
As far as I understand, the hop utilization is affected by the specific gravity of the wort. E.g, the Daniels formula for calculating IBUs takes the boil gravity into account. My only source is this ppt :)
Steeping grains does not substantially increase the gravity and should thus not affect hop utilization.
According to Daniels, brewing with a boil ...
You should be fine.
I always boil the hops normally (without a bag), then filter the boiling hot wort through cheese cloth to get the hops and protein out. After that the still very hot wort goes in a closed fermenting bucket and stays on the counter over night to get to pitching temperatures.
This works fine, but don't try to let unfermented wort sit for ...
Might be possible, if you are brewing two batches, one just after another.
If you will try to store wet hops, you are giving mold time to grow. Isomerisation continues to occur when hops are hot, so no way to dry them without loses. So then there is freezing, but that's troublesome.
If done fresh, from one brew to another directly, would work, but you ...
I use what would be my 20 min, flavor addition. My usual hop schedule is FWH, 60 min., and flameout and/or dry hop. I count the bitterness from FWH the same as a 20 min. addition because that's what it tastes like to me.
The bottom lime is that you're nor going to get a lot of hop aroma out of a 5 minute addition, or even at flameout. I've pretty much stopped doing those additions becasue I found, as you did, that they don't do much. Try whirlpool hopping or dry hopping for the best hop aroma.
How are you cooling the wort?
If you take too long to cool your wort after adding hops at the end of the boil, the high temperature of the wort may still allow isomerization, which would diminish the aroma.
What hops are you using?
Some hops do not make good aroma hops at all, they are bittering only.
How old are they?
The older a hop, the less aroma you'll get from them.
How do you store them?
If they're stored without oxygen, in a freezer, they will be fresher when you use them. The less fresh hops are, the less aroma they produce.
How do you ferment?
There are a bunch of factors to consider here. To name a few:
As you mention, zero to very little gravity will tend to increase the utilization rate as there will be less competitive inhibition from wort sugars.
Boiling in water alone will mean a higher pH (as malt phosphates, even in extract brewing, would normally react with hardness in/added to the water ...
You get so little bittering from hops added at 15 min. or less that I keep those amounts constant. Obviously, the IBU won't be identical, but it's close enough that you won't really notice the difference.
I use the IBU calculator at Brewer's Friend, it's quite quick and nifty. It also helps me as I have a different boil gravity than fermenter gravity and this effects the impact that the hops has.
It does however not deal with anything but alpha acids, the aroma I would believe is rather more difficult/unfeasible to calculate to satisfaction.