We know the size of the Mandalay's internals, the base hull mass (230T) and the characteristics of the FSD, so we can calculate its maximum possible jump range - and its jump range at all masses.
Because the Vulture has a hull mass of 230T, once you put EDSY in experimental mode (enable via Help) you can play with possible pseudo Mandalay builds, bearing in mind the Mandy has more internal slots than allowed by the vulture's setup.
For example, a 91.53 LY 'build', the biggest range I could get - in an impractical non-boosting ship that would surely be a misery to fly - which agrees with your calculation.