RM doesnt have any real armoring ability, so the standard 0.2-0.3" of belt and as much bulge as you can fit without losing any speed for torp protection.

ok thx you mate!

another question, in the other nations, i always play BB with manual fcs.. with RM, i have to do the same, or i can use Auto fcs? 

You can use auto if you like, but you'll suffer reduced accuracy, the inability to cross lines and a 20% exp penalty.

I understand why you might want to with some lower RM ships, but youre better off with manual really.

ok, i will go with manual fcs, i yet to reach the lvl xD

which BB line you suggest?

regina margherita or the other? 

i have Rm andrea doria, caracciolo (1919) and giulio cesare (1940)

so, i'll take still regina line?

With the AD you can avoid all the BB1-2's with only 2 main guns, so on that basis either line will do. But since the Caio Dullo still hasn't had its sprite enlarged , I'd go for the Regina still.