About a year ago we discussed this and decided to increase the
number of entries from 8 to 16 because we wanted the possibility
to add more physical machines in the future.  We choose this
setup because currently we only use 4 different machines.  Do we
no longer want this?

I agree that we should use more DNS domains.  But we need to use
domains that can be changed when a tracker is moved or removed.  
Can we do this with the vu domain once cs.vu.nl goes offline?  Do 
we have direct or indirect access to a third domain?