Still looking at some load levelling options (and haven't had the chance to crawl under the car and actually measure due to the rain!).
Does anyone know the internal/external spring diameter on the Stock rear Bilstein coil-overs ion the GT's?
At this point I'm thinking about some rubber doughnut spring spacers - either Mr Gasket (cheap)or Sumosprings (not so cheap) to overcome the laden sag. There are quite dodgy options like those metal raising blocks that jam in between the coils but I'm not going there.
Even if the doughnut style ones fit I'm not sure there is room between the spring and the damper on the Bilstein set up for the doughnut should it bulge inward at all - it may rub, so this may not be an option at all.
Plan B is to investigate some uprated King Springs - but again unsure if the higher spring rate will screw or improve the car balance unladen. (it may flatten the ride round corners I guess)