I have successfully used an old, old technique involving drilling holes in the barrel channel, soaking the stock in a water trough, and hanging a weight on it in the direction that you want it to move. I believe this technique is detailed in either Roy Dunlap's or McFarland's book on gunsmithing. Both of these are frequently found in public libraries.
I always routed a series of channels in the barrel channel afterward, and glassed steel arc welding electrodes into the stock to keep it straight.