I tried using the profile structure hatch set to colour 255 to mask them but the hatch masks the outline of the structure as well. Draw order would work on the structure but will not effect the hatch, even using draw order by colour does not work, the differeing colours are not displayed in the list.
You could change the profile structure type to a block and include a hatch object set at the back as colour 255 which would work but wouldn't be as good looking as the actual part type.