Form Finding of membrane structures

Hi, I am working on pneumatic structures and doing the form finding in SOFiSTiK by defining the prestress in the membrane and internal air pressure and also defining a volume inside the structure.

What I wanted to ask is:
I am changing the internal air pressure drastically and keeping other properties exactly same. Still the resulting tensile stress in the membrane remains same (Example below) -

  1. first image is the form finding result with 0.8 kN/m2 internal pressure

  2. second image is the form finding result with 0.4 kN/m2 internal pressure

Both have a resulting sigma of 1.83 MPa.
I wanted to see the change in the tension of membrane.

Question: why exactly the sigma not changing with changing the internal pressure (as form finding is the static equilibrium between internal air pressure and prestress in membrane).

I hope that I was able to explain my doubt.
Thank you

Never mind, I thought of the problem in different way. Understood what exactly was happening.
The doubt is solved.