In descr_settlement_mechanics
More means more growth
Code:
<factor_modifiers>
<factor name="SPF_FARMING_LEVEL">
<pip_modifier value="1.0"/>
<city_modifier value="1.0"/>
<castle_modifier value="0.90"/>
</factor>
<factor name="SPF_FARMS_BUILT">
<pip_modifier value="1.0"/>
</factor>
<factor name="SPF_HEALTH">
<pip_modifier value="1.0"/>
<castle_modifier value="1.0"/>
<city_modifier value="0.8"/>
<pip_min value="0"/>
<pip_max value="25"/>
</factor>
Edit Citadel to whatever you want or any other settlemnt.
Code:
<population_levels>
<!-- city -->
<level name="village" base="500" upgrade="1000" min="500" max="1500"/>
<level name="town" base="1000" upgrade="3500" min="500" max="5000"/>
<level name="large_town" base="3500" upgrade="9500" min="500" max="12000"/>
<level name="city" base="9500" upgrade="19500" min="500" max="25000"/>
<level name="large_city" base="19500" upgrade="30500" min="500" max="60000"/>
<level name="huge_city" base="30500" min="500" max="500000"/>
<!-- castle -->
<level name="moot_and_bailey" base="1000" upgrade="2000" min="500" max="1500"/>
<level name="wooden_castle" base="2000" upgrade="4000" min="500" max="5000"/>
<level name="castle" base="4000" upgrade="9500" min="500" max="10000"/>
<level name="fortress" base="9500" upgrade="22500" min="500" max="21000"/>
<level name="citadel" base="22500" min="500" max="30000"/>
</population_levels>