TraX topbox experience

[kallakaki]

I think that the original BMW topbox is too small, so I wonder if any of you have experience of the SW-MOTECH TraX topbox?
http://www.mo-tech.de/produkt/?produkt_id=1862.
Is it waterproof?
Is is sturdy or "flimsy"?
Is it better than the Hepco&Becker Xplorer aluminium case?
http://www.hepco-becker.de/_eng/pdf/Xpl ... fo%20E.pdf

Thanks!