quick advice on hop substitution

had a recipe for an ipa that called for 1 oz of 14% columbus at 60min and 1oz for dry hop. the HBS didn't have columbus so i got 3oz 9% centennial. (3x9 = 28. 2x14 = 28. AAU's about equivalent.) So, should I just do 1.5 at 60 minutes and dry hop 1.5oz, or should I go put 2oz in at 60 and dry hop with 1oz.

I think I'm going to go with 2oz at 60 minutes and dry hop with 1 as I don't think 1/2 oz will make much difference for dry hopping, but I want to hear other people's opinions.

I was taught 3 x 9 was 27, not 28...

14 / 9 = 1.55 oz at 60 mins...

Dammit! That's what I meant!

I guess my real question then is, considering it's an IPA should I put that extra half ounce in at 60 minutes to get a bit more bitterness out or put it in for dry hopping to get a little more aroma out. dry hopping won't impart bitterness right? Outside of maybe some perceived bitterness. Will half an ounce make much difference in aroma?

I'd do 1.5 @ 60, you'd be at about the same IBUs (52) and dry hop the rest. 2 oz would get you around 67 IBUsway more than 1 oz of the Columbus. Dry hopping an extra 1/2 oz will have less of an impact overall than using 1/2 oz more for bittering. (you can't have too much aroma in an IPA IMO)