I built a jig so I could run the forearm through the bandsaw and create parallel sides on the original stock. Then I built up a laminated saddle type piece that would be the addition to the forearm. You can see this in the first picture The laminations were glued with Gorilla glue and the completed piece was attached to the roughed up forearm with epoxy.
You can see that I also added a small flat piece to the butt stock toe area and then shaped both additions to suit. The pic of the modified stock in grey was with the textured finish before the black final coat was applied. The camera angle makes the forearm look wider at the tip but it isn't really. The bottom of the new forend and the bottom of the piece I added to the toe of the buttstock are parallel with each other and the bore line. It rides the bags great and shoots fine with a bipod. This stiffened up the forend also. I also glass bedded it at the same time.
This was really just an experiment and if it didn't work I had a new stock already picked out but the one in the pics is still on and doing its job.