You can grind it down with a belt sander or by one at a sporting goods store that is not so large. It needs to be a little oversize to match the stock angles as you grind it down. I screw it on the but of the removed stock. Put one layer of ducktape around the stock and begin freehand sanding it down on a belt sander. You need a steady hand if you slip you'll nick the stock. when you get it down to the tape just litely finish it up for a smooth line between stock & butpad.
Most pros put it on the butt, screw it down, mark it around the circumfirence of the stock, take it off screw it on a jig ( just a piece of 2x4 will work) you just need something to hold onto. Grind it down to your line remembering to follow thw angle of the tip of the stock. Screw it back on the stock as it gets close to check for fit.
Regards,