... : DaveJ61 Hi Martin, Thanks for this. This is absolutely jaw-dropping. What have I let myself in for? :-) I'm working some strange shift patterns this week, covering for other people but I hope to look at all this in closer detail at the weekend. Dave posted: 24 Nov 2018 18:00 from: Martin Wynne Some progress today on the S1 inner jaw. For dimensioning purposes I have split the inner jaw into two components. This part I have called the "stand": 2_241233_460000000.png It sets the gauge-face of the rail by locating the foot of the rail*. This assumes of course that the rail foot is the same width as the head. If not there will be a gauge_tweak setting to make final adjustments to the chair position. *vertical rail. I'm not getting into the madness of inclined rail, which in my view is unbuildable in small scale models. Behind the stand there will be an "web insert" component in the rail web, which will be dimensioned to match ...