Hi Stephane,
Sorry for delay in getting back on this. It took a while till I could dig through the code and see if there was an easy way to change the default.
Doesn't look like there is, so I added code to make clm and nlvls show up in the Preference pane where you'll be able to set them.
This change will be in the next version (probably next week).
The actual preferences get stored in a platform specific way specified in Java and (certainly on the Mac) are buried in a fairly inaccessible location.
Bruce