ship designs

It doesn't have any effect. It's just to provide extra slots for components.

Space Empires Depot | SE:V Balance Mod

Believe it or not, but even with the 3 levels I find myself running out of internal slots on small freighters. Is the amount and type of slots the same for every race or is it ship model specific?

Yes, it's ship set dependent.

Space Empires Depot | SE:V Balance Mod

It is actually ship model specific, but at the request of players, modders, and beta testers who complained about the unfairness of such a setup, Aaron added an override a while back to make all of the frigates use the same layout, all of the destroyers use the same layout, etc. The override is located a text file in the SE5\GameTypes\(mod name) folder; stock uses "Standard SE5" as its mod name. (I forget the name of the text file; it's something like Mod_Configuration_Settings.txt)

You'll probably want to start a new game before changing this, though, and it might also be helpful to make a copy of your "Standard SE5" mod folder and edit the copy, rather than the original, so your slot layouts don't get messed up in multiplayer games...

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The power of the ancients is now yours to command. You are truly the Master... of the obvious

Meh, it's in a PBW game with a custom shipset, but good to know, tnx.

Can't say I ever cared for the extra decks. I like seeing everything in one glance. Anything that adds more clicks to the game makes it more time consuming and less enjoyable (and that applies elsewhere as well).