Anyone have any luck using the Surface.Boundaries node. It only produces empty lists for me. Is there something that I’m missing?
It looks like this node is for boundaries that are in the surface definition. This is not necessarily for borders (outer edge of surface).
Try Surface.PerimeterCurves instead. 
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Nice one @jacob.small I tested this one and here’s my findings.
Short animated gif - Testing both nodes:
Findings:
Cheers,
Jowenn
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SmallSurfaces.dwg (4.0 MB) Thank you @JowennLua and @jacob.small for this tip. However, my findings are that this solution does not scale well. The attached dwg has three “small” surfaces by Civil 3D standards and using this method to get the perimeters takes a long time to process and ends up with errors.
Please post your DYN as well. Thanks!