I'm in the process of doing a model in which I integrate sets that are not from my home. I know the size and weight of the room... but it is complex, in multi-materials, etc.
So I was wondering if we had a way to force the weight of the piece (basically, make a simple slice and tell him "you, you're 60Kg")
Agree with @.PL's proposal, but be careful when you position your center of gravity !
If you use this info just for weight, no worries, but if you want to know the position of the CdG of the set in which you integrate it, you better ask your supplier for the XYZ coordinates!