Hi Ben,
Would you mind posting your code on stackoverflow:
http://stackoverflow.com/search?q=revit-api+revit
I’ll have a look a bit later
Edit:
I did give it a try. Unfortunately, it seems that Dynamo is incapable of initiating a proper “TopographyEditScope”. The python interpreter says that the TES is active, but any attempt to modify the input topo, results in an error. For reference, similar code executed in RevitPythonShell, runs without a hitch:
I suggest you file an issue report on this.