I bought a heavy bag a couple of months ago, and have been belting it every day. Now it has gone soft, progressively softer as the top of the bag is approached. I want to fill it and harden it up, any suggestions of what to do? I have heard wet newspaper, shreds of material or sand is good. Will sand just sink to the bottom and make it worse? Is wet newspaper just good for bitches with girl hands? What do you think is the best option? Thanks.