if your good with wood u could craft a wooden block to the size witch suits you and glue it to your stock and then when thats glued on and cured give it a final sand to shape it and then give it a coat of stain and varnish this is if your gun has a wooden stock but if your gun was £400 or over or its a pcp i would not advise it. now days you can go to a custom stockist witch can craft you a stock to your dreamed shape size but be warned this would be the expensive way out if u need tips i can post pics thats if going to try the home made option. hope this helps. if u think im being a rite div post me back on hoohed hunter. just so u know i have done this with one of my cheaper guns and it worked a treat.