I don't have the answer but I can suggest posting your request on the Inventables XCarve forum. I read it frequently and the folks there are quite knowledgeable and very helpful. Also please note that based on what I've read, it is critical that your PCB is perfectly level or that you run an auto level macro to compensate for any misalignment. I use UCCNC to control my DIY CNC router and there is an interesting YouTube video about an auto level plugin for that software. Search YouTube for UCCNC PCB Autoleveler Plugin to see how it's done.