For example, if you only had one marker with ID 4 being tracked you would need to add ppt.dls four times to get marker 4. Trackers 1-3 would not have any data.
Code:
tracker1 = viz.add('vizppt.dls')
tracker2 = viz.add('vizppt.dls')
tracker3 = viz.add('vizppt.dls')
tracker4 = viz.add('vizppt.dls')
Is it difficult for you to switch over to using VRPN?