good post on add-on recoil pad. I also made an add on recoil pad - not as nice as this one, but it worked OK. I did it just because I didn't want to train myself to flinch.

I just use a piece of pipe insulation. The tubular foam insulation (usually dark gray or black) that is split lengthwise to fit over water pipes. Comes in various inside diameters (I use the widest), and the foam is about 1 inch thick. Just cut a length of this to fit over the butt of your gun. The lengthwise split allows you to fit it over the butt and it just stays in place. This works OK for firing at the range but would not stay in place in the field. Unless you added the elegant touch of ..... duct tape!