Hi Guille, does it work better if you set "Output : Quads & Triangles" in the meshing options when you export out from MoI instead of "Output: N-gons" ?

You may also want to set a value for "Divide larger than" to dice things up into smaller pieces like this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2833.5

- Michael