As its posting may have been a little obscure:

https://forums.totalwar.org/vb/showthread.php?t=74083




border_horse.xml
Code:
<Model>
	<Type>Border_Horse</Type>
	<BoneMap>unit_models\BoneMaps\soldier_bone_map_new.xml</BoneMap>
	<AttachmentSet>unit_models\AttachmentSets\Final Kite.attSetXML</AttachmentSet>
	<AttachmentGroups>
		<Group>Cav Spear</Group>
		<Group>Sword Secondary</Group>
	</AttachmentGroups>
	<Meshes>
		<Mesh>
			<FileName>unit_models\_Units\EN_Peasant_Padded\EN_padded_basic_lod0.gr2</FileName>
			<Distance>11</Distance>
		</Mesh>
		<Mesh>
			<FileName>unit_models\_Units\EN_Peasant_Padded\EN_padded_basic_lod1.gr2</FileName>
			<Distance>30</Distance>
		</Mesh>
		<Mesh>
			<FileName>unit_models\_Units\EN_Peasant_Padded\EN_padded_basic_lod2.gr2</FileName>
			<Distance>50</Distance>
		</Mesh>
		<Mesh>
			<FileName>unit_models\_Units\EN_Peasant_Padded\EN_padded_basic_lod3.gr2</FileName>
			<Distance>80</Distance>
		</Mesh>
	</Meshes>
	<Torch>
		<Bone>bone_lhand</Bone>
		<OffsetX>-0.09</OffsetX>
		<OffsetY>0.0</OffsetY>
		<OffsetZ>0.0</OffsetZ>
		<WorldOffsetX>-0.35</WorldOffsetX>
		<WorldOffsetY>0.8</WorldOffsetY>
		<WorldOffsetZ>0.6</WorldOffsetZ>
	</Torch>
	<Textures>
		<Texture>
			<Diffuse>unit_models\_Units\EN_Peasant_Padded\textures\EN_Peasant_Padded_scotland.tga</Diffuse>
			<Normal>unit_models\_Units\EN_Peasant_Padded\textures\EN_Peasant_Padded_normal.tga</Normal>
			<Sprite>unit_sprites\scotland_Border_Horse_sprite.spr</Sprite>
			<Faction>scotland</Faction>
		</Texture>
		<Texture>
			<Diffuse>unit_models\_Units\EN_Peasant_Padded\textures\EN_Peasant_Padded_rebels.tga</Diffuse>
			<Normal>unit_models\_Units\EN_Peasant_Padded\textures\EN_Peasant_Padded_normal.tga</Normal>
			<Sprite>unit_sprites\slave_Border_Horse_sprite.spr</Sprite>
			<Faction>slave</Faction>
		</Texture>
	</Textures>
	<Skeletons>
		<Skeleton>
			<Mount>Horse</Mount>
			<Primary>MTW2_HR_Spear</Primary>
			<Secondary>MTW2_HR_Non_Shield</Secondary>
			<PrimaryAttachment>MTW2_HR_spear_Primary</PrimaryAttachment>
			<SecondaryAttachment>MTW2_Sword_Primary</SecondaryAttachment>
		</Skeleton>
	</Skeletons>
</Model>
For more details see the thread - WARNING Advanced Modders only (it makes my head hurt )
https://forums.totalwar.org/vb/showthread.php?t=74083