There are several slings that carry the rifle cross chest but still shootable. I think they are great for hunting in the woods, but too much in the way for other purposes. In Alaska I often carry mine in a saddle scabbard or cutdown case behind the right pocket of my ruck (the pocket is there for skis, but I have used it for lots of other long things over the years). The lever is to the back and the rifle muzzle down. I can draw the rifle (a 16.5 inch Marlin 1895) over my shoulder without moving the pack. This is almost as fast as a sling and much easier on the shoulders and the rifle. It is as good as anything except muzzle down behind the left shoulder in brush which is the other way I carry. It will catch, but not as bad as most carry positions. It might be a problem in crawling. It could slide forward or out if you got your shoulders below your rear.

Good luck,

Jerry

ps +1 on the condom, it works as well as anything I have found except light plastic pipe caps, but they are hard to find to fit your rifle. Use the unlubricated ones!