Joel Sternfeld always told our class to rate Portra at half the box speed, which meant in most cases running Portra 160NC at 80 and you'd BETTER use a tripod ("90% of the 'look' of art photography is the tripod.") His reasoning was that Kodak always over-rated their film, but this probably isn't really the case anymore. I wouldn't be surprised if some of the "look" of his work is due to consistently squashing the highlights in exposure.
I also recall overhearing a conversation where he was telling somebody that if they needed to do handheld available light, they should try using iso 800, shooting it 400, and pushing it two stops. Hahahaha.
My advise to the OP would have been about the same as everybody elses'. Just develop normally and be glad the film tolerated it. I do not agree with "Joel Sternfield" or any other teacher/know-it-all personalities claiming that they know better than the scientists at the film company who work very diligently to R & D their product. I guess I'm too old to be fooled anymore by some "expert" that claims to know better than Kodak.
Joel Sternfeld was one of those 70's types who was revolting from the saturated look of color by abusing color neg film for abnormally muddy tones; he did this in an interesting manner. But the published box speed is indeed the correct location of first base relative to what the film
is engineered to do. How you bend the rules after that is up to you. Just remember that, in this respect, Portra is a lot more forgiving than Ektar will be.
It wasn't my intent to diminish this Sternfield fellow's classes or students. Perhaps I have a sensitivity to teachers and professors who sop up a paycheck teaching gobbledegook. My brother-in-law is a retired professor who managed to make quite a nestegg for himself teaching absolute boloney that not a soul in this world needed to know. It taints my attitude towards some of these "scholars" who bloat college budgets and tuition costs with make-work absurdity.
And then I think of a guy like PE who dedicated his career as a scientist at the film company whose job it was to print a reliable box speed on the product, then hold quality-control to that standard. So, between the 2, I'd say Kodak is more reliable than some subjective relativist egghead like my brother-in-law.
I had a mixed experience in college. The humanities professors thrived on total BS. But I did a lot of independent study and research in sciences
under some of the best of the best. Any so-called art professor probably would have shot me after a few weeks. ... they were the most
stuck-in-a-rut types of all (the more avante garde they got, the more they all looked the same, painted the same, spoke the same, etc.).
Technique and craft can be taught; art requires some kind of native instinct, which would be vastly aided if the entire term for "art" was
erased from existence. Personally, I've found Kodak's graphs and tech data sheets on these color neg films to be spot on.