got ours down to 1360kg.... as shown recently in HPI car retains all front trims including carpet,headlining and even sunvisors. Both doors are as per factory items including mega weight in door intrusion bars. Only really deleted heater box, air con system, hicas system and ABS. Only body deadner inside from b pillar rearward removed and none under car has been stripped (yet).
so sub 1300kg may be achieveable.
Also...that cage looks very close to what Gibson Motorsport ran in their cars.