I noticed that there's an attribute missing in the export of the skin controller in the 3dsmax export plugin:

library_controllers > controller > skin > source(binding)

the source used for binding is supposed to store a 4x4 matrix for every bone used in the skeleton, when exporting, it gives me:

<source ...>
<float_array ... array of floats describing 4x4 matrices >
<technique_common>
<accessor source="binding-table" count=3>
<param name="INV_BIND_MATRIX" type="Float4x4"/>

the problem is that <accessor> seems to lack < stride="16" > as I've seen in other sources with 4x4 matrices, and missing this attribute is causing me some troubles (I should do a hack in order to read the source properly)