Well, what you have shown so far is not even having the tech. You changed some of the wording for a hull description in the GC2Types.xml file.
And you did it incorrectly, to say the least.
If you copy the code section into Notepad and use the Edit-Replace function to change all the < to [ and all the > to ], you can copy and paste it in to the reply.
Then it looks like this:
[Hull Name="HugeHull2"]
[DisplayName]Huge[/DisplayName]
[Description]Huge Hulls are for those mega ships. A Huge Hulled ship is over 3,000 meters long. They require 6 logistics points to coordinate so few fleets will have more than one of these. This would be the flag ship of your empire.[/Description]
[Cost]160[/Cost]
[Size]80[/Size]
[SensorRange]4[/SensorRange]
[HP]50[/HP]
[Model]Huge_2[/Model]
[Thumbnail]Huge_2[/Thumbnail]
[Speed]1[/Speed]
[Category]Huge[/Category]
[Logistics]8[/Logistics]
[Tech_Requirement]Massive Scale Building[/Tech_Requirement]
[/Hull]
Using this example, changing it to a Gigantic would look something like this:
[Hull Name="GiganticHull0"]
[DisplayName]Gigantic[/DisplayName]
[Description]Gigantic Hulls are for those supermega ships. A Gigantic Hulled ship is over 10,000 meters long. They require 10 logistics points to coordinate so few fleets will have more than one of these. This would be the ultimate flag ship for your empire.[/Description]
[Cost]300[/Cost]
[Size]160[/Size]
[SensorRange]4[/SensorRange]
[HP]120[/HP]
[Model]Huge_2[/Model]
[Thumbnail]Huge_2[/Thumbnail]
[Speed]1[/Speed]
[Category]Gigantic[/Category]
[Logistics]10[/Logistics]
[Tech_Requirement]Gigantic Scale Building[/Tech_Requirement]
[/Hull]
If you do it with the original entry then that particular ship will move over to the Gigantic category. If you copy, paste and modify the section you will have the same ship model being used for two different category hulls, and it will show up in both lists, each with their respective capabilities.
But, like I said before, if Gigantic does show up with its own tab one of the others will be squeezed out.
You also need an associated Gigantic Scale Building tech defined in TechTree.xml.
In TechTree.xml you would have something similar to this added:
[Logistics ID="Gigantic Scale Building"]
[DisplayName]Gigantic Scale Building[/DisplayName]
[Cost]3500[/Cost]
[Description]Allows us to begin construction of Gigantic hulled starships.[/Description]
[Details]Gigantic hulled ships are the latest engineering masterpiece to come from our scientists. A subspace field helps hold the ship together and they can really take a beating in a fight.[/Details]
[Requires]Large Scale Building[/Requires]
[Category]Hull[/Category]
[Model]lrgbuilding0[/Model]
[AIValue]50[/AIValue]
[/Logistics]
Correct spelling and syntax are extremely important, so don't make the mistake of replacing an underscore with a dash like you did in the last line of post #4. And don't change or add pointers to models and thumbnails that do not exist.
Modeling ships is another ball of wax altogether. It requires both the correct programs and the required skills. There are ships available for download that can be used, though.