Do you mean like this?
Have been using the topbox virtually every day for past 2 1/2 years.
Upside - Seems to hold all I want to put in it!
Downside - Now looks very scabby and corroded (the piccy was taken when new!), although the frame still looks OK, unlike those for my H & B panniers. The box hangs off the back some distance which represented a problem recently when recovered in the back of a van, and wouldn't fit, so had to remove the box.......leading the final issue....the lock holding the box on to the rear rack gets covered in all sorts of s**t and took some beating and oiling to release. Obviously this would be negated with a proper maintenance and cleaning regime!
Hope this helps
Regards
Dazlove