I just pressed copy on this ship:
Hollow (Spark) class Stealth Carrier 45,000 tons 845 Crew 12191.9 BP TCS 135 TH 960 EM 0
6666 km/s Armour 1-112 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 78 PPV 0
Maint Life 1.53 Years MSP 8128 AFR 337% IFR 4.7% 1YR 3929 5YR 58931 Max Repair 4050 MSP
Intended Deployment Time: 12 months Flight Crew Berths 310
Hangar Deck Capacity 15000 tons
1200 EP Inertial Fusion Stealth EcoDrive (5) Power 1200 Fuel Use 7.31% Signature 192 Exp 7%
Fuel Capacity 6,690,000 Litres Range 366.0 billion km (635 days at full power)
Cloaking Device: Class cross-section reduced to 15% of normal
Strike Group
30x Spark Beam Fighter Speed: 38400 km/s Size: 10
This design is classed as a Military Vessel for maintenance purposes
And that got me this ship:
Hollow (Wisp) class Stealth Carrier 44,300 tons 845 Crew 12048.1 BP TCS 132.9 TH 960 EM 0
6772 km/s Armour 1-111 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 78 PPV 0
Maint Life 1.55 Years MSP 8159 AFR 327% IFR 4.5% 1YR 3871 5YR 58063 Max Repair 4050 MSP
Intended Deployment Time: 12 months Flight Crew Berths 0
Hangar Deck Capacity 15000 tons
1200 EP Inertial Fusion Stealth EcoDrive (5) Power 1200 Fuel Use 7.31% Signature 192 Exp 7%
Fuel Capacity 6,690,000 Litres Range 371.9 billion km (635 days at full power)
Cloaking Device: Class cross-section reduced to 15% of normal
Strike Group
30x Spark Beam Fighter Speed: 38400 km/s Size: 10
This design is classed as a Military Vessel for maintenance purposes
I changed nothing. In design view, the original has 6.3 Biphase Carbide Armor, and the copy has 6.2 Biphase Carbide Armor.
So they have the same armor tech. (Although I am researching the next tech level at the current time).
Where does the 700 ton difference come from? Like I say, I really did do anything except press the copy design button.
I experimented by trying the new armour button on both the original as well as the copy, to no effect. I gave both a point of armor, and took it out again. Again, no change, still 700 ton difference.
Is there a hidden factor over time that allows for the construction of smaller ships? The original design was made a decade ago..
EDIT: I did get better shipbuilding rate construction tech, would that matter? Although that still would not explain that I can't get the old design to match the copy.
EDIT2: I found it. Pressing the copy button turns off the 'keep spare berths' option. It has less flight crew