Line width in sp maps

Hi,

I am trying to change the line width in (shape) maps
produced using sp package, but without success.
All my attempts with lwd parameter failed.
I found a brute force solution to save the map in
EPS and change the linewidth there - but I would
expect that there is a regular solution.

best regards,  Vladimir Batagelj

Vladimir Batagelj, University of Ljubljana, Department of Mathematics
  Jadranska 19, PO Box 2964, 1111 Ljubljana, Slovenia
http://vlado.fmf.uni-lj.si