I was aware of some of the projects, including yours and the one you linked. I decided to move away from solar balloons, as you wouldn’t be able to both insulate them well enough and have them collect solar energy. Toward the end I decided a useful product might be a tethered electrically heated advertising platform. But how useful is that really? And a hydrogen balloon would work better for that anyway.
This convinced me to stop, for now. All that energy input for so little performance:
http://aeroix.de/fileadmin/user_upload/aeroix/redakteure/Dokumente_HeiDAS/2007AIAAHeiDASUH.pdf