PS. With the rigidity concern in mind, I did run a little "marker" cut - to put a 20mm long slot in a piece of MDF to act as a place marker. I then MDI for 100mm along an axis. Then run a second marker cut, and measure the distance between the two markers. This meant that the axis being measured was completely stationary during cutting. The measured error between markers was very much present. So again this suggested to me that the less than ideal rigidity was not my main issue here......