Allright, thank you Alexey.
So I would like to keep the interpolation to not get a lot of holes in my DEM (removed buildings etc) and still keep the edges sharp. So if I understand you correctly I can just create a shape around the area I want to export inside, but where do I choose this from the export menu? I can only see the setup boundary settings which I presume uses the bounding Box coordinated?
And since we're talking about exporting, how do i make the no data section transparent, and not solid background?
Thanks a lot for all the help