... intersection with the centre-line of the chair does not coincide with the centre-line of the timber: 2_180233_350000000.png I know it is only a small difference, but the human brain being what is, even a small offset from being central within the timber width is very noticeable. And in most prototype cases, wrong. However, as you can see, I think I have got it working. regards, Martin. posted: 20 Jan 2016 23:42 from: Martin Wynne Hi Andy, Another progress report. 2_201814_250000000.png 2_201814_490000000.png A few notes about this. Initially this is going to be restricted to the REA bullhead designs for switches A to D, with hard-wired chairing data. Partly because I have the full chair designs for those, but mainly because a complete customized chairing implementation is going to be a massive task and other things are more important first. I still have a lot to do -- the L1 bridge chairs, check rail chairs, crossing chairs. The P slide chairs are always aligned to the stock rail, ...