If I knew how to get PTC to do anything for me I'd be rich. Or at least happy. Or happier. A little. Maybe.
I suspect that Warren Buffet would have a difficult time getting PTC to do anything for him. Looking at the direction PTC's products have gone it is likely PTC's own people can't get PTC to do anything either. Looking over the wall, a few MathCad users might agree.
But why you would use a known crippled drawing package to try to do plant layout when you can put the same effort into using the 3D part of the software and get the answers you want is ... interesting.
The technique to find planar areas is easy -
Check the Math Insight website for Green's Theorem for an explanation. There is an article there called "The idea behind Green's theorem"