Nit-pick a 400T Type R

[Condottiere]

It's more of an issue of how many hardpoints you can cram into a given volume.

 

[Sigtrygg]

Surface area is more important...

 

[Geir]

Surface area is more important...

Not by the rules, just by reality. I wish we still had to preallocate space for hardpoints - eat the tons as part of the design, even if no turret was installed. (And yes, that would mean if you only allocate space for a turret, then you can't install a barbette... or a bay)

 

[Sigtrygg]

Take a look at the ship design system in GT:ISW - it gets hardpoint allocation by surface area correct in a more abstract way than FF&S.
It may be worth a JTAS article - my original posting to CotI with regards to surface area and hardpoints actually pre-dates GT:ISW so with a bit of work could be adapted to MgT ship building.

 

[Condottiere]

Hardpoints are to reinforce an area, usually against the recoil of a specific calibre gun(s).

One reason you don't see armed merchant cruisers with larger than single six inch guns.