Large plot on .005inch dura-lar . registration problems

[johnbougs 0]

I have been trying to cut a large (57x20inches) for a on .005 inch thick dura-lar sheet for a re-usable stencil.  Normally I use this material as a for a cutting mat for other materials (with a repositionable adheisive to hold the stock) I frequently do 24x36 inch plots on lighter materials this way.   First I tried this methode for cutting the material, but after it cut the outline it was out by a couple of inches.  Thought maybe it was the weight of the material, so thought I would "etch" the outline then manually cut the shape.  The outline was still out by about 1/8-1/4 inch. 

 

Any suggestions?