I'm not an auto body expert – but work with enough mates who are experts. That is what they tell me, all of the time.
They make a sealer that works great in that case – but I can't think of what they are (I don't work in that area often enough).
Silicon sealer likes to be under pressure and does fill in the minute gaps between gaskets and metal surfaces (like timing cover gaskets for example), when left in a fine film (not in a big bead, like many people like to do).
Matter of fact, for gaskets, like timing covers for example, put a bit on a gasket, take a finger (or something) and spread it out to a thin film. Not much of it is ever needed.
You may be good, and hopefully so. I'm just going by what I've heard.
