I also received my FR10 yesterday. It also hisses. I haven't taken the chassis out to see if it's been modded at the factory. But I don't really care to take it out of the cabinet to check when I've got a V2 incoming soon. I think that I'm pretty high on the list.
I debated a long time about whether to get the FR10 or FR12. I was concerned that I would lose too much low end with the FR10. But I don't feel like the low end is lacking. I might feel differently after I do a side by side with my EV PXM-12a, but I can already tell that the FR10 is good enough for my needs. All in all, I'm completely satisfied with how the FR10 sounds.
Now all I have to do is be patient as I wait for my pair of V2 preamps.