A vessel such as a balloon or the rubber air-cell of an inflatable boat will become more rigid when pressurised.

The same must happen to the fuselage of a pressurised aircraft - but to what extent?

Unlike balloons and inflatable boats, aircraft are not flaccid when unpressurised...

I imagine that the effect must be so tiny as to be not just utterly negligible, but literally impossible to measure; is it possible however to calculate theoretically (and if so, of what order is it likely to be)?