Rhodes,

I'll not display my ingnorance of physics as, clearly, your grasp of it is greater than mine.

However, given that it's a bit late to add weight to Felix's action, adding weight to the buttstock seems to be about the best fix for a muzzle heavy gun available.

I have seen reference to adding weight as far forward in the buttstock as possible. Thereby getting the added weight as close to "between the hands" as possible......and I'd say that this approach is used due to the principle that you describe.