Seems like using a button on the butt was not as common on American rifles as it was on European built ones. Most survivors that appear to have been equipped for swivels had a hole drilled in the triggerguard. If I recall, that triggerguard has quite a bit of meat at the front of the bow. A bow on the fore end to accept the other end of a sling would not be that noticable in my opinion and most of the ones on the market are mounted with a bolt so you can remove it. It is not a particularly light gun, a sling would be a nice option. But, if it is your rifle, do what you want, and the heck with what anybody else thinks.