MeshVS_ElementalColorPrsBuilder, MeshVS_Mesh::computeSelection()

Hello forum,
I generated and visualized a volume mesh of a solid, made of first order tetrahedra.
I'm able to dynamically select and highlight the volume elements using an elemental
color presentation builder (MeshVS_ElementalColorPrsBuilder) and issuing

AISContext->Activate(meshIO,MeshVS_SMF_Volume); [1]

where meshIO it the mesh interactive object. See Picture00 for a demonstration.
The same holds for the surface mesh elements (triangles; not shown).

This works also for a second order tetrahedralizazion: see Picture01, in which tetrahedra
midside nodes are shown: dynamic highlight, and selection work as expected.

For a fully hexahedral, first order, mesh, as shown in Picture 02, dynamic highlight and selection this works:
see Picture02.

If the hexahedral mesh is made second order (20 nodes for each hexahedron) the detection
mechanicsm fails: no element is highlighted when mouse move, and obviously no selection
is made possible.

Some observations:

First of all I realized that in MeshVS_Mesh::ComputeSelection(), because of the three lines

MeshVS_Buffer aCoordsBuf (3 * aMaxFaceNodes * sizeof(Standard_Real));
NCollection_Array1<gp_Pnt> aPntArray (aCoordsBuf, 1, aMaxFaceNodes);
TColStd_Array1OfReal aPntArrayAsCoordArray (aCoordsBuf, 1, 3 * aMaxFaceNodes);

aMaxFaceNodes shound be set at least to 20, using

aHBuilder->GetDrawer()->SetInteger(MeshVS_DA_MaxFaceNodes,20);

(aHBuilder is the presentation builder set as highlighter) since these 20 nodes
are exactly the ones used for building the "sentive polyhedron".

For the moment my attempt for making possible highlighting and selecting hexa20
has been

1) feeding the highlighter not with the second order mesh but with the downgraded
first order mesh

Any suggestion?
Grazie