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1: I need to rotate the grid slightly to align to my spline and can't find a a global rotate setting, only local rotate.
There are a couple of ways you could rotate the Ceiling. Firstly you could rotate the actual RailClone object and then reapply the spline, it'll clip the style using the new orientation. Secondly you could use the Generator's Clipping Area > Z Rotation property
2: I want to limit the 'light' bits of geometry from reaching the spline edge. Only the plain ceiling tiles should collide with the border
At the moment there is not an automatic way to achieve this as RailClone's has no way to detect whether or not a segment has been sliced. However you might find the workarounds in this post helpful: http://forum.itoosoft.com/index.php?topic=2502.0
3: And lastly i'd like to adder a border around edge of the spline area which then contains the ceilings within that.
This can be achieved by adding a new L1S generator to the style and using it to create the frame. Just use the same spline as the A2S generator is using as a clipping area and the two will always stay in sync.
I hope that helps, please let me know if you have any further questions.