Interesting thing, i guess it is not just a Huntsman problem, but an overall.
I never really cared for the FPS thing.
But i was doing same now as Huntsman, running trought the Ultima Shoppingstreets and HUB.
From start i had 50FPS, then it droped in Hub to 20 and while running through the streets it droped even to 11.
So i have same problem, but just don’t get that much bothered by it.
Maybe i am already playing too long with the problem and i got used to it somehow.