Dear riverGIS team,
I tried the procedure you report on your website and everything went smooth in Linux environment (Ubuntu 14.04), from the database creation (which is easier than windows) to computing cross-section elevations, however as I try to export the sdf, the created file resulted without any extension and not loadable in HEC-RAS. HEC-RAS does not seem to recognize anything. Then, I repeated the same procedure using your plugin in QGIS for Windows and magically it works fine. My idea is that the created sdf file in linux might have some problems with encoding, or perhaps some tabs placed in wrong places, I don't know, but this my experience. Unfortunately I can't paste the results here because data are not publishable yet.
Hope these feedback might help you in further releases, it's a great tool!