67 headliner ...puzzled

I did mine in the garage and it wasn't 70 degrees either. More like 50. The car was gutted and painted. Once I got it hung in place, I threw the car cover over the top and placed a 500W halogen light pointing upward towards the liner. Got it nice n toasty w/less wrinkles when stretched in place. The heat in the summer months will take care of the rest of the small wrinkles.