Hi Martin, as you recommended I tried to use MeshMath -KWMtoPolyData to attach my p-map to a mesh.
Unfortunately I did not work properly. Could you please give a quick look at my data? I'm sure I committed a trivial error somewhere.
Here is the code:

MeshMath f1_pp_surfSPHARM_procalign.vtk outputMeshwithMap.vtk -KWMtoPolyData results_rawPval.txt MapName

I also attach the relative sample data.

Thanks again for your support, it's being fundamental for my analysis.

Marco