Only the head of the model doesn't get dismembered. It stays when I set "NPC to Dismember Head" to true.
Here's the contents of the model_default.skin file:
head_cap_torso_off,models/players/stormtrooper/caps.tga
heada_cap_torso_off,models/players/stormtrooper/caps.tga
hair,models/players/jaina/head.tga
head,models/players/jaina/head.tga
heada,models/players/jaina/headc.tga
head_cap_torso_off,*off
l_leg_strap,models/players/jaina/torso_body.png
torso_collar,*off
torsoa,models/players/jaina/torsog.tga
r_arma,models/players/jaina/torsog.tga
l_arma,models/players/jaina/torsog.tga
r_handa,models/players/jaina/handsp.tga
l_handa,models/players/jaina/handsp.tga
r_leg_strap,models/players/jaina/torso_body.png
torso_cap_head_off,models/players/stormtrooper/caps.tga
torso_cap_hips_off,models/players/stormtrooper/caps.tga
torsoa_cap_r_arm_off,models/players/stormtrooper/caps.tga
torsoa_cap_l_arm_off,models/players/stormtrooper/caps.tga
l_handa_cap_l_arm_off,models/players/stormtrooper/caps.tga
l_arma_cap_l_hand_off,models/players/stormtrooper/caps.tga
l_arma_cap_torso_off,models/players/stormtrooper/caps.tga
r_handa_cap_r_arm_off,models/players/stormtrooper/caps.tga
r_arma_cap_torso_off,models/players/stormtrooper/caps.tga
r_arma_cap_r_hand_off,models/players/stormtrooper/caps.tga
l_leg_jedi,models/players/jaina/torso_body.png
r_leg_jedi,models/players/jaina/torso_body.png
hipsa,models/players/jaina/legs_green.tga
r_lega,*off
l_lega,*off
r_lega_cap_hips_off,models/players/stormtrooper/caps.tga
l_lega_cap_hips_off,models/players/stormtrooper/caps.tga
hipsa_cap_r_leg_off,models/players/stormtrooper/caps.tga
hipsa_cap_l_leg_off,models/players/stormtrooper/caps.tga
hips_cap_torso_off,models/players/stormtrooper/caps.tga
hips_belt,models/players/jaina/accesories.tga
hips_holster_r,models/players/jaina/accesories.tga
hips_holster_l,models/players/jaina/accesories.tga
hips_belt_buckle_f,*off
hips_belt_buckle_b,*off
