Try editing the unit.xml. It can usually be found in the units folder in the mod folder. To clarify, you can edit the number of a class by changing the "numSlots" variable in the <Class> Part. So for example, the class is <Class name="ExampleClass" nameUI="@ExampleClass_name" description="@ExampleClass_desc" numSlots="2" supply="100" iconTex="data/textures/gui/deploy/ExampleClass.dds". Just change the numSlots value to the amount you want. Please note that you would need to make a new unit for it to take effect.