Almost the same suggestion - and the way I'll use it:
Don't fiddle with too much details in your CAD-program. This should be used for the general design of the pit. Graphics belong IMO to a dedicated program like Gimp, Photoshop,...
So, export (somehow) the faces of the panels and fine-tune them in Inkscape/Gimp/...
The result should then be ready to print 1:1.
Depending on the level concerning the design of your pit, you'll surely need more than only one program. For me, I'm trying to master Sketchup, Gimp, KiCAD for the complete Pit. That altogether is a quite long road, but I like to learn that kind of new stuff.
Sure, there are other ways to skin the cat. ;)