You have to mod both export_descr_unit (EDU) and descr_model_battle. (DMB)
Change the stats of the unit in the EDU following this example

type mongol infantry
dictionary mongol_infantry
category infantry
class heavy
voice_type Light_1
soldier mongol_inf, 40, 0, 2
officer mongol_officer
attributes sea_faring,can_sap,hardy
formation 1.7, 1.7, 2.2, 2.8, 7,square
stat_health 1, 0
stat_pri 12,9, no, 0, 0, melee, blade, slashing, sword, 0, 0.7
stat_pri_attr ap
stat_sec 0,0, no, 0, 0, no, no, no, none, 25, 1
stat_sec_attr no
stat_pri_armour 7, 6, 0, metal
stat_sec_armour 0, 0, flesh
stat_heat 1
stat_ground 2, -2, 0, 2
stat_mental 14,disciplined,trained
stat_charge_dist 40
stat_fire_delay 0
stat_food 60, 300
stat_cost 1, 600, 250, 160, 140, 600
ownership germans

Then mod DMB this way:

type mongol_inf
skeleton fs_swordsman
indiv_range 40
texture data/models_unit/textures/MONGOLINF.tga
model_flexi data/models_unit/mongolinf.cas, 8
model_flexi data/models_unit/mongolinf.cas, 15
model_flexi data/models_unit/mongolinf.cas, 30
model_flexi data/models_unit/mongolinf.cas, max
model_sprite 60.0, data/sprites/spain_choson_archer_sprite.spr
model_tri 400, 0.5f, 0.5f, 0.5f

There you are. let me know if you experience problems