Yes, 13 inches is a bit short but, as I recall, some military M98 Mausers weren't much longer than that and standard sporters are often only 5/8 inch longer.

This might be a bit old-hat and boring but what if you kept the rifle for shorter people and stick one of those old slip-on pads over top of the existing one when you need to use it? Still too short? Try a quarter-inch strip of rubber inside the slip-on as well. The slip-on pad's side rubber would at least help protect the stock when out hunting.