Magic sites questions

[Stormbinder]

Ok, question for Dom2 veterans: Does anybody know the exact terrain modifiers for magic sites and how do they work?

I know that land types such as Mountains, Forest, Waste, Swamp increase chance of finding magic sites in the province, with Mountains being the largest modifier.

I also know that Farmland decrease that chance, and Plains have no modifiers.

So let's say that we are playing on magic 50 setings. If I understand numbers correctly that means that "Plains" province have 50% chance of
having magic site in each of it's possible 4 slots, correct?

Now does anybody know how much Mountains and each other "good" land types add to this 50% chance?

Also what are the calculations if there are more than one terrain type present? Do they add? Multiply? (Like in case of Mountain/Forest/Farmland province for example)

Finally what about sea provinces? Do they have magic site frequency same as Plains?

Usually I cast 8 water gems underwater spell on each of my water provinces as soon as I can, but should I also cast all non-elemental type of search spells, looking for nature, death, astral, blood? Obviosly there are different names for the magic sites on the survace and underwater, but is overall effect still the same? Or do sea provinces tend to have more water-producing sites but less nature (or other types) producing sites?

And Last question - I think it is possible for province to contain more than 4 different sites, I've seen it now and than. Does it only happen due to random event (like with random event that gives you new Mine site for example, or Earth Caves, etc.)? Or "magic level 0 sites" (the one that you detect automaticallly when you conquer the province - like Library, Arena, etc.) do not count toward "max 4 sites per province" limit. Or both?