NIPPY BAR???

[daveg]

Its difficult to be certain from the pictures but I think :-

1) The bodywork between the upper edge of the boot lid and the passenger compartment (the part underneath the stowed hood) has been cut away.

2) The drivers seat is particularly far back and if the replacement seats are the same size as the originals there seems to be more
room behind the seats than normal.

3) There is no sign of the raised curved section to give clearance for the diff in the raised luggage area behind the seats.

4) The prop shaft tunnel has either had a repair or an extension.

5) The vertical floor-pan step behind the seats has been moved backwards to give more storage space / room for the seats to sit 
further back. I wonder if the  "tall 'boxes' over the rear spring housing area" that Jon E refers to are the remnants of the old vertical edge.

6) If the floor pan has been extended backwards the bar could be above the area of the original support from the chassis extension
to the luggage area and may be an attempt to strengthen the rear end or address the problem of a "drooping rear". 

I think all Nippies and 65's had rubber mats rather than carpets so the cutout you mention would not have been original.