How to store gear/ammo in the stock of my rem 700?

[streetstang67]

I thought about getting a pack to strap on the butt stock of my rifle, but then I realized that it is probably hollow inside the stock itself. How can I easily store stuff in it?
It is a Remington 700 sps dm (synthetic stock)

 

[streetstang67]

I found an example of what I'm looking to do (at least one way to do it)
it was in the thread "show off your long range rifles", posed by 'Terrill'