I did the same thing about 10 years ago when I bought my 835. I took some styrafoam, cut it to fit the inside of the hollow stock. Put about 4 oz of lead shot in a sock, duct taped the sock all over and inserted it in the very end of the stock and topped it off with a Limbsaver. It does help to balance the gun and definitely reduces the 3.5's recoil down to a 20 guage.