Soo, in my last game I have come up with an idea.
Playing with Yorian tech tree I could quickly get Advanced Materials upgrade, giving me access to Reinforced Hull Point.
Then I outfitted a Cargo Hull with 5 of those, taking up 15 out of 66 of its space and giving it 25 bonus HP.
In other words I had a ship with 26 HP and 51 units of free space before any other race could even get close to medium hulls. Its rather obvious I filled this space with weapons and armor, making a battleship outclassing anything other races could come up with. Moreover, after they level up a bit I could change Reinforced Hull Points for more weapons and still have bonus health given by experience. Its like having a large ship without having a large ship. Moreover, those "pocket battleships" performs pretty well compared to medium ships and has a similar price.
What'cha think about it?