I did this on my Rem 700 SPS. I used a chunk of clear fir, and I hogged out a shape on the band saw before I sanded it to fit. Worked fine.
Since this was not a "walking" gun, I epoxied a couple of pounds of lead shot into the stock cavity before I installed the spacer.
Then I made a cheek piece out of the leftover wood, and got it to fit pretty well. Took all the sting out of the .300 Win Mag (even with max load 210 grain Bergers), and I shot it a lot better.
Only problem is that I got hooked on working with wood - ordered a couple of cheap ($99) laminated stocks over the internet, glass-bedded them (which works way better on laminate than on tupperware), and so on, and so on.
Once you realize how easy it is, you'll want to do all your tupperware stocks, so a $15 piece of douglas fir can lead to $500 worth of laminated stock "raw material". I've since re-stocked, pillar- and glass-bedded my .375H&H and built up a nice little mountain rifle in .270Win. Eventually I'll get around to my .416 Ruger, but like I say, it's a slippery slope.
Bill