the 3 arguments to the
viz.rotate command is yaw, pitch, and roll. So just make
ROTATION_INC the second argument instead of the first.
Code:
#Turn Up or Down
if viz.iskeydown(viz.KEY_UP):
viz.rotate(viz.BODY_ORI,0,-ROTATION_INC,0)
elif viz.iskeydown(viz.KEY_DOWN):
viz.rotate(viz.BODY_ORI,0,ROTATION_INC,0)