Slic3r question - gap in perimeter?

I'd like to precisely measure the height of layer 1... so I'd like 2 concentric circles with a 0.2" gap between them... is there a way to get slic3r to do that?

 

Slic3r isn't where you want to do that. Instead you need to create a model that has a height precisely what your first layer is supposed to be. Then when you slice it, slic3r will make it a single layer.

You could also take a look at this. If configured correctly using OpenSCAD, it makes a bed level test object that is the height of the first layer.

http://www.thingiverse.com/thing:15709

 

You could also make your skirt wider by increasing the loops. Your measuring error will get smaller this way as well.