What does the fuel tank look like on a 86 Pontiac fiero?

The fuel tank on an 86 Pontiac Fiero is a plastic, somewhat rectangular tank located in the rear of the car, behind the rear seats and above the rear axle. It's not a smooth, uniform shape; rather it has some contours and likely some bracing or structural ribs molded into its plastic construction to add strength. It's not easily visible without removing interior panels or raising the car. Think of it as a relatively shallow, wide, rectangular boxish shape, not a cylinder like some cars.