As far as hopping goes, 4 oz of bittering is A LOT. Chinook is a great bittering hop by itself, no need to waste 3 oz of cascade and get an overly bitter beer. If I were you I'd probably go for something like:
x oz Chinook - 60 mins (whatever amount gets you to however many IBUs you want, probably 1-1.5 oz)
1 oz Simcoe 15 min
1 oz Cascade 5 min
1 oz Cascade 1 min
2 oz Cascade Dry hop (though in my opinion 1 oz is usually enough)
And all of that is assuming a full gravity boil. If you're doing late addition full boil or half boil, adjust as necessary.
IPAs are all about bittering and finishing hops, with the emphasis on finishing. Most people like to do 60 minutes for bittering and wait until 15-0 to add the rest.