I am considering between wall mount and ceiling mount (cassette) mini split units. It seems that all cassette units are suspended. From the installation guide of a cassette unit, it noted that there is a small gap between the unit body and ceiling surface, and the gap is covered by the grille of the unit. I wonder, though the gap is covered by the grille but it is not sealed, would such gap becomes a source of air leak from attic? This means that dust and insulation material would enter into the living space from the non-sealed gap?!