Import RAW Rectangular Terrain Heightmap

I am trying to import a terrain heightmap, that is of rectangular dimensions. It seems, however, that the required sizes of imported heightmaps need to be of square dimensions. For example, 2049x2049. As a result, what happens in this case, is that the terrain imports, but it has a flat surplus area to fill out the 'rest of the square'.

Is there any way to 'slice off' the extra terrain after importing, when importing a rectangular raw image? Better yet, is there a way to just make it accept non-square dimensions from the start? Do I need a script to make this happen?

Thanks!

 

Did you find an answer? I am trying to do the same thing, and no luck so far.