The UP! software doesn't allow for raft smaller than 2mm. But you can still disable it.
Compared to other slicers I have used (Kisslicer, Skeinforge) the UP! raft is very thick !
The UP! raft structure is made of tunnels and so far it has proved to be efficient. But making such a thick raft is a big waste of material ! (could it be a commercial strategy ?)
Let's see how to print with just a single layer raft...