I am right eye dominate, but ever since I can remember, I've always shouldered a rifle (whether it was pretend, a toy, or real) on my left shoulder. Trying to shoot a long gun from my right just feels weird and awkward. I also shoot pool left-handed, and I kick with my left foot too. However, I play the guitar right-handed. And, while I practice firing my handgun with both hands, I carry it on my right side. I liked the double gun rigs when playing cowboys as a kid (who wouldn't want two guns instead of one), but I don't remember wishing I had a single left-handed holster over a right-handed one.