I've not got etended storage but would have thought the net linked to works just on the 4 hooks - the one in my mini did and looks pretty similar to the one on the ebay link (but smaller
but seems to hook on ok ). I thought extended storage was the plug in rail thing (so not a 'net'?)
The sport line boot liner I've got does a pretty good job at stopping stuff sliding around (due to grip on the surface) so it may be another thing worth looking at rather than changing the boot floor?