Light cruiser armour configuration

[scaffold]

Hello everyone!
Another one of my newbie questions if you don't mind.
What am I supposed to gain by my scientists unlocking the Light Cruiser Armour Configuration? I don't find any changes in the ship design options when it happens. I am most likely missing something. Can you please explain?

[dorn]

Before that, you can only have protected cruiser armour scheme for "light cruisers".

After that you can use same possibilities as for capital ships, mostly sloped deck, flat deck and with AoN available even that.

The protected cruiser armour scheme is lighter however it protected much less than any other.

You can look there:
en.wikipedia.org/wiki/Protected_cruiser

You can see that even if citadel is not penetrated, there can be hits that could cause flooding above citadel.
Another thing is as armour is sloped with increase range you lost advantage of angle as shell starts to hit armour with lower angel.

So protected armour scheme is good for early century cruisers when coal bunkers protect ship above citadel in some way, hits are relatively on flat trajectory. This can make reasonable saving the weight of armour but later and especially with oil fired ships and long range gunnery this type of protection is usually not satisfactory and other schemes provides better protection per weight.

[scaffold]

Thanks!
I didn't realise it was illegal to have anything other than Protected Cruiser configuration for CL before this advance.