problem with findedges and skeletonise

[thejasvi]

Hello,
 
I have two square-like wire frames with 60  and 80 cm perimeters (20 cm a side).
This make the expected perimeters of the two frames  1.33 (80/60=1.33).

When I create outlines using a segmented line and measuring, I get the expected ratio of perimeters.
However when I run the  (processed and binarised) images through the 'Findedges' plugin  - the 'perimeter' output (using ctrl+m) does not correspond even closely to the expected ratio!

Could you please advise me on what I'm missing out ?
Here are the two images :


PS. I have also tried using the 'analyseskeleton 2d/3d' - but it gives no sensible output when I run the first wire-frame, perhaps because of its 'open' geometry?

 
Thejasvi