11" deck will bounce shells from BB4 and below.

I hope you are aware that when your opponent shoot at you at max angle (40 to 45 degress), even 12" deck cannot help you. To start bouncing shells, you have to move closer so that they have to shoot you at 30 degrees. When you position yourself there, you can bounce BB5 shells with even less armor. 

Well the right way to play a battleship is to dodge shells and not to bounce shells... I know little about AWing a Lion 2, because it only makes the ship less good.

Have you tried playing the Lion 2 with three guns, 0.2 belt and max bulge for 39 knots? Try to wiggle your ship and avoid turning broadside when the enemy still has the fire, only turn broadside after he missed you.

Someone else can certainly tell you how to armor it, but it will make your Lion 2 a sitting duck.

Okay.  Thanks for the feedback guys.  Like I said, this is my first BB5 and I need to find the strategy that suits me best.  I haven't tried your setup joris92, but I will and hopefully it goes well.

All you ever wanted to know about shell damage, effects of armor on shell damage, effects of torpedos based upon amont belt etc..

http://fm.en.kupaisky.com/Community/Forum/View.aspx?num=14883&searchtype=0&pagecount=0&searchvalue=shell&sort=5&category=D01&page1=1

Read it then read it again.  

** Standard Disclaimer: some information may be out of date ** 

Enjoy the Game. 

The right way to protect most BB is by dodging shells, but there are three notable exceptions: Lion1 (2 gun setup), Lion2 (2 gun setup) and Queen Victoria. The reason is that UK armor is the only type of armor that can bounce BB45 shells. With 10" deck you can bounce most BB1234 HE shells and 11" will bounce most BB5 HE shells. You should rely on dodging when fighting another BB one-on-one. However, if you rush in you will become the target of many BB1234: you need that deck armor to survive.

In GB, your primary duty as a L2 is to rush, not to line fight. You should point your bow toward the enemy to minimize your profile. No other nation on your team can spearhead the rush without dying. So I would put always deck armor on, treating it as a big asset for your team.

I never used armor for the L2 (or any UK BB except QV) and it was great ship. I could get consistent games with 100K attack. SW L2 is most balanced of BB5s, good for both offensive and defensive playstyle.