blackrat - sorry for mixing up the X and Y axes. I expect that you mean the X axis according to my new drawing? Maybe it is better, but it will also reduce the effective Y-axis work length. Anyone to comment on this?

JAZZCNC - with respect to extending the top rails (Y-axis), I am not quite sure what you mean by "placing gantry in space using a short cantilever"?[*]With respect to BOB - I have noticed that you are not happy with cheap Chinese boards - and very understandable so, if you have had bad experience with them. My reasoning was that the signal "processing" (Smoothstepper) is the critical part and that the BOB is really a fairly simple device which is not so likely to fail or give problems. A concern with the PMDX 126 (which is undoubtedly very good quality) is that it does not have controller for spindle and pump.