longtom,
I've used my bench belt sander to grind to fit a few recoil pads. Don't remember using your brand of pad. Usually had a new 120 grit or higher belt on it when fitting the pad. Sanding belt can heat up rubber, causing it to melt, but if you move lightly across rubber and don't stay on one area too long, not a problem. I assume mounting pad on stock is with 2 screws. Suggest you mount pad on butt and then rough in the pad to the wood, being mindfull of the slope of stock as it continues thru pad. When roughing in, don't try to get pad level with the wood to avoid hitting wood with the belt. Then use something to mark outline of butt on back of pad. Remove pad and then continue your grinding, being careful to grind the pad with correct angles/contours of the butt of stock, till you are near the line you've traced on back of pad. Example: lets say the bottom edge of the stocks butt has a 5 degree angle to it as it continues from the wood and goes thru the pad. So, if you want to follow the slope of the wood thru the pad, allow for it when grinding pad. When you get close to line you've traced on back of pad, reinstall pad check your work, remove pad and continue grinding. May want to do this reinstall and recheck a couple of times to get fit you are happy with. As for the so called final finishing/sanding of the pad, I have used either a block of wood with sandpaper wrapped on it or one of the "mouse type" electric sanders. Do tape off the wood next to pad to protect it if you do the final finish/sanding with pad installed.