I have a coral beauty in with my porcy and they're fine. My case might be an exception though, since my fish is rather lazy and soon realized that begging at the top of the tank is a lot less work than picking on anything in the tank.
I've never had chromis before, (Although I've thought about getting a shoal of them for my 100gal if anything happens to my tomato)but I've read about them and I know that even maxed out, they're still bite sized for the puffer...even if they weren't, it still wouldn't bother the puffer a bit to bite them in half and eat them in two bites. Any fish you have in with a porcupine puffer has to be too big to fit in its' mouth one way or the other...There aren't a whole lot of cases of the fish being too long, they've got very powerful jaws.