Mn12, with an anisotropy barrier close to 65 K, has been for 20 years a prototype nanomagnet, but in spite of a number of investigations the actual link between the value of the effective barrier and the complex pattern of intra-molecular interactions could not be clarified. Mn12 has already been studied by INS. Although the cross-section is expected to discriminate different parameter sets, the use of powder samples and of variants of Mn12 with several inequivalent isomers, and the lack of PSDs, prevented to individuate the form of the spin-Hamiltonian.We intend to study a recently synthesized variant of Mn12 containing a single high-symmetry isomer, for which high-quality single crystals are available. By exploiting the PSD of LET, we will extract the detailed form factor for several transitions. We expect to make a decisive step-forward in the comprehension of this archetype system.