[Gimp-user] (Mis?)use of jigsaw filter

[Allan Topp <ad707 ncf ca>]

I love the output of the jigsaw filter and would like to use it to laser 
cut some jigsaw puzzles.

However I have been unable to produce the obligatory single 0.001" line 
that the laser cutter requires.

Customarily I would use Inkscape to produce the final cutting template 
but Inkscape treats the GIMP produced image as two lines with fill 
between them.  Removing the fill is simple but, of course, leaves the 
double lines.

Does anyone have a solution in GIMP - or indeed in Inkscape - for this?

Much appreciate any assistance.

TIA