... the dummy vehicle with the spacing-ring attached is a convenient way to check the spacings. But to work against the adjacent rail like this, the ring inner diameter needs to be set according to your track gauge. For 6ft way 44.67mm centres, the settings are: P4 68.67 mm EM 69.3 mm 00-BF 16.5 71.0 mm 00-SF 16.2 71.3 mm If you find the calculation troubling, you can set up some tacks at the required spacing, zoom in and adjust the ring size visually by mouse action. 2_260808_320000000.png At B you can see that the 6" clearance envelope on the vehicle is conflicting, but the actual body sides are clear with about 6" (2mm) between them. That is a bit tight, allowing for different vehicle dimensions (the above is using the default settings), body sway, wheelset/gauge freedom, offset bogies or axles, and other variables in a model. Prototypically it is too close, but you may decide that it is acceptable to avoid reworking the track plan. You could try ...