PJ...
Take this for what it is worth as it is coming from an amature-I would do the following: Wrap two layers of masking tape around the stock at the point where the pad meets the stock. You can get a special type of tape used for masking cars,etc for painting that releases easily and leaves little residue. Finish grinding or sanding the pad as necessary to get it where it fits to suit you being careful to not sand through both layers of tape. Using a 3M sanding pad (sponge like deal with two different grits) apply WD-40 for lubrication and smooth the edges of the pad to suit your preferences. Again, be careful to maintain at least one layer of tape to prevent damage to the stock. Wipe clean, remove the tape and residue and enjoy!