I do a hop stand/whirlpool beer where I add all the hops at flame out. My point was that the temp drop would be well below 185F before the 90 min. was reached ,so no more isomrization at that point.
How is the bitterness in the beers when you do this? Do you have a guesstimate of ibus?
The beer is Cream Ale, and it is a knockoff of Pelican Pubs Kiwanda Cream Ale, and all of the hops go in after flame out. They claim 25 IBUs.
For 10 gallons of a 1.050 beer, I have estimated 13% extraction. I you look at the data from Tinseth, this is roughly an 18 minute addition, I think I have used 15 minutes as the whirlpool with a March pump is not as vigorous as at a commercial brewery. The hops I have used are Mt Hood at 4.8% and 8 Oz for 10 gallons, and it is estimated to be about 25 IBU. I like the results.
I have thought of doing an ultimate late addition IPA using high AA hops at flameout. This might be an ispiration.