Does it get as bad as OpenSCAD? I found that anything even remotely complex using OpenSCAD brings the machine down to a crawl. And I'm on an overclocked 5930K with 64GB ram ;-)
I'd be very curious to see a couple screenshot of your project! I used Google Sketchup to do landscaping last year around my house; I wonder how this would compare...
sketchup plan: https://goo.gl/photos/Qc5mEnFiFm9UWBvv8 reality: https://goo.gl/photos/Gn66MSc8UPshR3CC8