Sorry for being so late.
With ground objects like ships the durability is a combination of the object's "EmptyMass=" with the volume of the object's "Hit Boxes". This durability level can then be amplified by the use of the "StructuralFactor=" entry. It can the be further modified via the "HasArmor=TRUE/FALSE" option. Then setting a "ArmorMaterial=" and thickness value in millimetres.
Armor material types are ALUMINUM, STEEL, TITANIUM, GLASS, FIBERGLASS, WOOD, and NONE
An example from a battleship.
[Hull]
ModelNodeName=Hull
EffectSize=1.0
MinExtentPosition=-16.634,-105.707,-8.412
MaxExtentPosition=16.634,114.828,9.093
StructuralFactor=1000.0
HasArmor=TRUE
ArmorMaterial=STEEL
Armor[FRONT].Thickness=304.8
Armor[RIGHT].Thickness=355.6
Armor[LEFT].Thickness=355.6
Armor[REAR].Thickness=254.0
Armor[TOP].Thickness=273.05
Armor[BOTTOM].Thickness=254.0
Take a look at this post, is included quotes from the games creator about hit points and armor.