Cyborg, that’s the other article I had talked to about! It was on a different server though, but it’s the same article; I just couldn’t find the URL the other day. 
I pronounce it “mang-nus”. And we have discussed this here before: see here.
Just yesterday, on a TV show from Mexico (here in California we have plenty of channels in Spanish), the people in the show sang “Ave Maria” in Latin. The vowels qualities were crystal clear. Not concerning length, the five vowels, sounding just as in Latin, were there. It was like music to my ears (well, they were singing) hearing everything pronounced in such a way that resembles the Classical Latin pronunciation. The Italians would have pronounced everything in nearly the same way, except that they would have pronounced “gratia” as [gratsia], while the singers on that show said [gratia], as in Latin of course. They pronounced the Latin mostly as if were Spanish, and thus didn’t sound exactly like the Classical pronunciation, yet I’d rather hear this anytime than the English aspirated T’s, P’s, and K’s, the French and German guttural R’s, or the Nuntii Latini’s [kva], [sva], and [gva].