Create two configurations, one with all the holes suppressed and the other with all the holes un-suppressed. You can then created two configs of your assembly, Holes/No Holes referencing the appropriate part configs.
1. You can then compare volumes of the part/assembly between the configurations to compute a volume percentage.
2. You can pick the surfaces that the holes open on and compare their areas.
I am curious, though, why do you need this information?
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