It should not be necessary to make any modifications to the coordinate system in Vizard. Try testing with the following script after specifying the correct hostname:
Code:
import viz
viz.go()
viz.addChild('piazza.osgb')
opto = viz.add('optotrak.dle',0,'192.168.0.114')
body = opto.getBody(0)
viz.link(body,viz.MainView)
This
video tutorial is quite old but it may help with the optotrack setup.