Dude tbh if you usually chill but you just cant for this batch I would NOT brew a double IPA with the NC method...
When I started out I was a notorious no chiller, did it with every brew, and it was great, saved alot of time and water, but the one thing i noticed when i started using the chiller was within a few minutes of the chiller running the smell from the kettle almost vanished, where as whenever I no chilled I could smell malt and hops for ages after!
Now my thinking is, if you cant smell all the aromas when the chiller starts running, then this aroma must be being trapped in the beer, and for me at least the finished products show this - much cleaner more prominent hop aroma in the chilled beers, and no IMO dry hopping does not make up for a 0 min addition, the characters are completely different...
I think in terms of bitterness being able to tell the difference between 30 and 40 IBU would be quite hard, because the perceived bitterness is allways going to be different between recipes.. Ive had two beers side by side that are both the same OG, FG and IBU but one can seem more bitter than the other - I did an experiment once with a NC beer, small starting gravity, no hops in the boil and a big addition at 0 mins, no chilled, fermented, and what do ya know - the beer was bitter, so there was definately utilisation happening!
Hope that helps, sorry for the rant lol :icon_cheers: