Adding Weight to a Figure, Advantage or Not?

[Shabby J]

I just replied to a thread started by Broncoman about the weight issue and while typing trying to keep with my thoughts as they were flowing, I came up with a question, as follows:

Take a custom figure based up at 3.8 grams for instance, could he be at a slight disadvantage if going against a Miggle bigman that had weight added to him to equal 3.8 grams?
Those experienced in tweaking and that have an understanding of base/figure physics may be able to use the ability to add weight to a figure where they need it, thus making for a more effective tweak, in turn making a better running, more powerful player than the custom figure at 3.8 with no weight added.

This is possible right? I would appreciate anyone's feedback/experience with this.