We often hear this question from future customers. Usually they are asked people in the process of getting acquainted with the information on the PVC ceiling and other types of ceiling finishes.
The minimum distance between the main and suspended ceilings is 3.5 cm (height of the ceiling profile). Provided a perfectly flat main ceiling!

But most often on the main ceiling there are bumps or differences in ceiling plates, or a slight inclination of the plane. Therefore, based on our experience, we lay 2-3 cm indentation from the main ceiling – for horizontal alignment of the plane of the future stretch ceiling.
Total, on average, the stretch ceiling (the fabric of the finished structure) will be 5-6 cm below the main ceiling.