Thanks for the link to that very interesting paper John, it confirms many design principles I would love to implement - oh that someone would gift me full copies of ANSYS and Solidworks... and food & rent for 6 months whilst I learned to use them to their full advantage The idea of filling adjustment gaps had crossed my mind - more from the rigidity aspect than damping (I will be doing the damping elsewhere), but it raised the question as to what do you do if something moves?? Lots of pretty rigid machines (much more rigid that the likes of most forum members would ever make) have tramming adjustments, and I've learned over the years to always check (and if necessary adjust) machine alignment regularly if you want good cuts. With the sort of machines we're making having a lot (probably too many) bolted joints there's a lot of scope for things to drift when pushed hard.