On a Hogue stock for a .308 I have, I used some steel threaded rod about 3/8 dia..cut a channel in the fore-end with a dremel and glued it in with some epoxy. No more flexing using a bipod.

The Tupperware stock's recoil pad comes right off and you could fill it with anything...plumbers putty works and is reversible.
I have not noticed the Savage stock flexing as much, but it's only a .22.