Putting equal sized washers on each action screw would (theoretically) not induce any additional stresses, BUT...remember that the surface to surface fit that is most important in most systems is the fit between the recoil lug and the recoil lug web.
In changing the fit of the action to the stock with washers, you WILL change the relationship between the recoil lug and it's web. That may not have a huge effect depending, but it can't ever be a good thing.
