Our ph2 172, with Composite Seats, no rear seats, no airbags, anti vibration block or tar based sound deadening, with half a tank of fuel, the spare turini & tool kit and two people on board (weighing 85kg & 68kg - my athletic figure
) weighed in on the local weigh bridge at 1180kg.
The weighbridge has an accuracy of +/- 20kg.
So without people and tool kit/spare wheel (aprox 25kg?) it is almost bang on a 1000kg with about 25L of fuel on board.
Shaving another 100kg off a ph2 would require Polycarb, Composite Panels/bonnet and minimal rear interior for starters IMO.