Printing which respects DPI setting of the image

[midora]

I did a plugin to render paper models (prisms, pyramids, stars, ...) to make some kids happy. The plugin requires that you print the nets in the exact size defined in the plugin. But I was not able to get the correct results.

 

Is there something I'm missing in the printing setup? Also printer+ doesn't seem to allow this.

 

Or do I have to add such functionality to the plugin (or maybe better to a seperate one)?