Here is how I have been doing my modding.
First thing download the ForgeTools
https://www.sinsofasolarempire.com/downloads.aspx
Then click My Computer
Then click Tools
Then click Folder Option....
Then click View
Then click on Show hidden files and folders and un-check Hide extensions for known file types then click apply and OK
Next extract the ForgeTools1.1.rar on to your desktop or any where else, then go to the follow directory.
C:\Documents and Settings\your user name\Local Settings\Application Data\Ironclad games\Sins of a Solar Empire\Mods.
Make a new folder call Test Mod in the Mods folder.
Then copy the ReferenceData from the extracted ForgeTools1.1.rar into the Test Mod folder and the rename it to GameInfo
( ReferenceData ) TO ( GameInfo ).
Now open up the GameInfo folder and pick a capital ship, I have use the CAPITALSHIP_TECHBATTLESHIP.entity for a example. Open the file with notepad go down the file and till you come to this part below.
slotCount 50.000000
BuildTime 75.000000
MaxHullPoints
StartValue 3000.000000
ValueIncreasePerLevel 120.000000
MaxShieldPoints
StartValue 1250.000000
ValueIncreasePerLevel 135.000000
HullPointRestoreRate
StartValue 1.500000
ValueIncreasePerLevel 0.100000
ShieldPointRestoreRate
StartValue 3.000000
ValueIncreasePerLevel 0.200000
ArmorPointsFromExperience
StartValue 5.000000
ValueIncreasePerLevel 0.450000
and change it like this below.
slotCount 5.000000
BuildTime 7.5000000
MaxHullPoints
StartValue 300000.000000
ValueIncreasePerLevel 120.000000
MaxShieldPoints
StartValue 125000.000000
ValueIncreasePerLevel 135.000000
HullPointRestoreRate
StartValue 300000.000000
ValueIncreasePerLevel 0.100000
ShieldPointRestoreRate
StartValue 125000 .000000
ValueIncreasePerLevel 0.200000
ArmorPointsFromExperience
StartValue 5.000000
ValueIncreasePerLevel 0.450000
then save and close the file.
This should make Tech Capital Battleship very hard to bet and fast to build and only 5 supply slots, oh are don't forget to enable the Test Mod to try this out.
I hope this helps, let me know how you get on with it. 