As seen in the attached pictures to this posting,
the resulting buckling margin (0.115) calculated
by Hypersizer does not coincide with the margin
(0.5791-1=-0.4209) calculated by MSC.Nastran FE
I calculated the margin using in-house tool
which uses Rayleigh-Ritz method, but it gave me
the margin -0.4094, which is around FE analysis
I don't understand where the difference was originated.
This panel even doesn't have curvature, so I don't
think that big difference is a possible case.