AutoCAD Inventor :: Mass Properties Recalculated When Use Feature In IAM

To get net weight of my parts i have one template that uses the volume x density and to get the gross weight I use the real dimensions of the item (a rectangular plate  without any cutting, e.g.) and then calculate x density, this way i can get both weights, and how in the most of times I need the gross, I overwrite the MASS PROPERTIES of each part with my gross weight. It works fine because all the assemblies sum the MASS of each part (that is over writed by the gross weight).

Now my problem:

In many cases when I need to use the same part many times with just a few of different details, instead of copy the part and change it, I use the same part, and in the IAM I use one feature to make this part different (like a chamber, small extrudes or even holes). But now I realized when I do this (feature in the IAM), it doesn't sum all the MASS properties of each individual part anymore ... it recalculate all the mass with the new IAM volume (with all the features)...so, in my BOM I got all the parts with the correct gross weight, but my total mass comes with the NET weight (and considering that I need the GROSS, i got the wrong mass).

Is there a way to change the way that inventor overwrite this mass in the assemblies ? with Ilogic, or even some Inventor's option ?