For me, the only hesitation with the 512 is the faux patina. If you don't mind it (or like it), there's much to like with the 512.
As for size, the 512 is a beefier 42 compared to the wire lug Radiomirs like the 337/338, thanks to the 1940 Radiomir's lugs, so, if it sits well on you, I wouldn't be too thrown off my those saying that 44 or 47 is the way to go. That being said, a 45mm Rad with wire lugs should also fit well --- see the 190 or 210.
The 392 is an okay option at 42, but, it's still pretty thick.