Svg format interpretation

I have written an exportAsSvg function for a program I am working on and would like to point customers to inkscape as an ideal editor.

 The files open fine in any web browser but in inkscape the stroke-thickness of the graphics are hairline thin.

I am using stroke thickness as a % value and I believe that is the only issue:

<rect x="-1375.925000" y="893.075000" width="1.850000" height="1.850000" style="fill:none; stroke:red; stroke-width:0.1%;"/>

The file is here <a href="http://student.cs.ucc.ie/~mod2/inkscape_prob.svg">link</a> with one of the lines enlarges so I can see it in inkscape

As far as I can see there is a large difference in rendering between inkscape and other programs, Does anyone have any answers to this??

Thanks,
Mark