I don’t have a heated bed for my Makerbot so I realize that using this material will warp a lot. That being said: is there a way where it won’t warp SO much?
Use a hair dryer to heat the bed and keep the model warm. This will reduce the warp a bit. Depending on your hair dryer.
I haven’t played around with nGen so I only give you my opinion, my suggestion would be to get a small sheet of polycarbonate and print onto that. I have printed ABS on it with no heat and it has worked. You can also try acrylic.