The 3 gun setup does work on the L1. I have managed to use it effectively many times. It does have a slight range disadvantage but its not massive. Are you using the lvl 91 16" Ls?

yes i'm using right guns, my gunners are lvl 98 with accuracy and reload capped. i done  both bb line so my crew is a little over BO level.
When i was on h39 i found that L1 couldn' t hit me at all, but i tought they just were all noobs. Now using L1 myself i found the range is really low.
in the last GB i done a 1v1 vs an RM bb4, he had more range, more firepower, faster reload...  i had to runaway before get sink.
That RM BB4 also has more Structural Strengt...
And this is the problem, Why Lion has BB1's structural?
Vanguard with more range has also lot more structural o.O

Structural strength is a meaningless stat, that as far as we know does very little if anything.

The main stat that determines how hard you are hit by large shells is your max displacement. The L1 has about the lowest max displacement of all BB4 iirc, which means that large shells also hit it for less than any other BB4.

My take on this (it's been a while since I played L1 so I'm probably wrong):

 - At level, L1 is best SW with 2 gun setup.

 - At later levels (after your crew is too fat for speed cap) 3 gun setup is nice.

 - AW setup is often touted as a fix-all, but IMHO - it doesn't fix anything. Can be fun if you prefer to torment single ships rather than win battles.

Sorry Alex but you are largely wrong about structural strength.

Take the Soldati I with 46 structural strength, equip it with the DD3 ( heavy) engine and it looses the ability to OH below about 5030 DP ( out of 8100), or 62% DP remaining.
Compared to the Z31 with 45 structural strength equipped with the DD1 ( heavy) engine and it looses the ability to OH below about 2890 DP ( out of 7400), or 39% DP remaining.

The ship with the better structural strength looses OH a whole lot earlier.
Interestingly the overheat damage for the Soldati engine is 36%, and for the Z31 engine it's 60%. Now the "overheat damage"stat may not be the stat that puts the limits on when a ship retains OH, but it is for sure not structural strength.

Btw all RM DD's loose OH that early, if you use the heavy engines. It gets better with normal engines and best with the light engines. As it happens those have progressively better "overheat damage" stats.

Based on personal experience, the L1 is a good bb4 with many possible set-ups.
3-gun set-up is my personal favourit, as you can go 44 knt and deal a lot of damage.
Playing it AW makes it slow and will make you sloppy when you change to another nation without armour.
If you play it with 3 guns, the key is to either wait for the enemy bb to be blind, or rush single bb's. While rushing them, the L1 can easily take out any bb, even a bb6;)
Dont try to line fight other bb4 or higher, just have faith and dare to rush sometimes if possible:)