When hunting , I keep the stress off my 76 yr. old shoulders by reducing the weight hung over them. Only time I use a powder horn hung on the left side , is at the range , with a brass free flow valve on it , to fill a powder measure. Hunting ,, I have one of the ugliest small hand made powder horns affixed under the pouch flap out of the weather. Like from old times , each gun I have , is served by it's own pouch The pouch , and horn , can vary as to the situation. Back to the original question , larger horn on the left side , and pouch always on the right side. My preference.