Thank you Jonathan. Yes, I'll make sure the steppers and drivers are beefy enough. I haven't done any CNC yet, but I used to plot PCB artwork on a Roland plotter and I know what you mean about all the stops and starts and changes of direction. Dovetails have more friction than ball bearings, but unless there's a similarly solid XY table out there with ball bearings, my guess is that it's easier to compensate for high friction by beefing up the steppers, than it is to compensate for a less-than-rigid (aluminium) ball bearing table of the kind I have seen being offered by the oriental suppliers, some of which look a bit flimsy to me. But I confess to a total lack of experience.

I hadn't even got as far as worrying about minimising toolpaths, and I'm going to have to print off your two examples and lay them side-by-side to ponder them. Obviously there are things to learn about this CNC business! Is there a good book out there which deals with subjects like toolpath optimisation?

Ian