I don't know can help,
but I in our studies, where I need to represent fluid passages as solid, but without calculating the weight, I am using configurations.
that is, in those components that could be recalled in db or displayed in the table, but of which I do not want to make the weight, I create a fictitious configuration, e.g. with name massacre, to which I associate mass nothing (it can be done by forcing the mass properties and choosing to do it only for the selected configurations), then I configuro in the axieme (or in a specific configuration of the axieme) the component loading precisely.
in the paper mill
$prpsheet:"mass"
and I make sure that the first view of the tree is the one with the set-up in which the piece is mass zero.
for my purposes for now works.
greetings,
a.