Well yeah you can convert one to the other but that assumes perfectly evenly distributed force over the given area and an unyielding plate for both, as well as the entire cell returning the equal and opposite force.Oh, that’s news to me. I never saw any documents on the details of the test and I didn’t think anyone here had uncovered those details. PSI vs kgf is irrelevant however (as it’s the same).
However, it does not directly translate when you consider that the cells bulge from the center.
The force at the middle at full charge will be higher than the force at the outside as it expands into the plate and increases locally.
So as I said before the springs are a compromise on constant pressure while maintaining a similar "flat plate" style of force application while the poron is a compromise on overall consistency of delivery applied across the cell in favor of space savings.
In both cases the force directly in the center will increase as it expands, perhaps even far beyond the "x psi" applied as the total force stays basically the same during the test, so my vote is for space savings.
If I did this in my basement for home use a good long set of springs and plywood backed up by an aluminum plate would be my go-to as space is less critical.