Overexposing the background is 2 stops is nothing for current negative films.
You see, I keep hearing this everywhere. I'm far from being an expert in film photography, but my experience (only a few rolls) is that the skies will get overblown with 2 stops or sometimes less of overexposure. I'm not saying that everybody is wrong, I'm just stating what my experience have been so far.
“Photography is a love affair with life.” Burk Uzzle.