Probably some of you people already do this but I find working backwards with my hop additions helps when. I'm building a hoppy pale ale. I know how much hops I like to use late so I calculate those first and work backwards to my bittering charge so I end up hitting the IBU # I want
I do something similar. But I’m no longer doing 30/20 min boil times so it’s a bit easier
I like doing the 30 minute bittering charge. I don't use my bittering hops at 30 but something that I feel lends some flavor generally something older that I need to use up. Fresher stuff goes in at the end or WP
Working backwards makes things much easier. You can design the late additions to get the hop aroma and flavor profiles you want, and then set the bitterness with early hops without having to worry about affecting what you already did.