You may have done your own research, but if I may add my 2¢, I think you're overpriced. It was a stretch to see sigs going for 140-150k, and that would be 40k over for a car that you can get RIGHT now and is limited edition. I can't see someone paying 40k on top of base price in advance to get the car in 2 months. If they're that patient, they can put an order in now and wait, or they can offer someone 40k to take their car right now.
For a GP, if you want a premium, I'd say 20k might be doable if the car is in hand.