ttersu, what version do you use? I've only got 1.0, and it's full of bugs!
So, I cut it out, and then cheated on the hollow part -- I spied a coping saw I hadn't used for years hanging on the wall, and thought hmmm, bet that would be good on foam. And it was.
Of course all this could be done with a hot wire, but I'm off those these days. Don't like the smell in the house, and it's too cold outside to move out there. Besides this has to be the simplest model imaginable. So what better to attack with blunt instruments?
Drew a line around a best-guess add on layer shape -- I'll be adding a piece of scrap pink 9mm Owens-Corning fanfold foam both sides.