Daz, I also tried your code and it works great! However the fact that I have to raise the Z axis manually makes me a little nervous. I know the popup box tells me to do that, but I could envision a scenario where I'm just not paying close enough attention and forget to do that.
I inserted a mc.mcCntlGcodeExecuteWait(inst, "G90 G53 G0 Z0.0") right between the two "end" statements, and now when I hit cycle start, Z goes all the way up before continuing. Just wanted to throw that out there if anyone is looking to do the same.