I have edited all my unit sizes.
Assets\XML\Art\CIV4ArtDefines_Unit.XML
Open this up in a XML editor, I think you can even do it in notepad. You will see this
<Type>ART_DEF_UNIT_LION</Type>
<fScale>0.61</fScale>
<fInterfaceScale>1.3</fInterfaceScale>
<NIF>Art/Units/Lion/Lion.nif</NIF>
<KFM>Art/Units/Lion/Lion.kfm</KFM>
<SHADERNIF>Art/Units/Lion/Lion_FX.nif</SHADERNIF>
<ShadowDef>
<ShadowNIF>Art/Units/01_UnitShadows/LionShadow.nif</ShadowNIF>
<ShadowAttachNode>LionBip Spine1</ShadowAttachNode>
<fShadowScale>1.0</fShadowScale>
</ShadowDef>
<fBattleDistance>0.35</fBattleDistance>
<fRangedDeathTime>0.28</fRangedDeathTime>
<bActAsRanged>0</bActAsRanged>
<TrainSound>AS2D_UNIT_BUILD_UNIT</TrainSound>
<AudioRunSounds>
<AudioRunTypeLoop/>
<AudioRunTypeEnd/>
</AudioRunSounds>
</UnitArtInfo>
<UnitArtInfo>
This is the one you want to edit <fScale>0.61</fScale> lower the number to make them smaller, riase it to make them larger. The above example would change the size of the Lion.
EDIT or just wait untill I release mine
