Hi carlosppamaral,
It's possible. I used the standard HD character that is included with Vizard. To make the body of any HD character invisible, open it's .cfg file, and look for the name of the material file for the body. The characters have a different file for the head and for the body. It's the name of the file that you should put in the avatar.visible() part of the code.
Code:
import viz
viz.go()
avatar = viz.add('vcc_male2.cfg')
avatar.visible(0, 'male_body.crfx')