Both hands free might be good today, but when your life might depend on how fast you can get that smoke pole into action, is factored in, across the saddle sounds pretty good to me. I can't recall how many guns I've seen with the forearm worn through to the ramrod channel, from being carried this way. One such gun was a Ballard Pacific, built long after scabbards, and shorter barrels, were common. But, grizzlies were still around in California at that time as well.
Hungry Horse