As far as carrying a scoped rifle I prefer the military sling which offers stable positions to shoot off hand or propped up.I carry the rifle with both arms or in the crook of one elbow.
for a Double maybe something off the hip might be nice with no carrying sling but enabling support from the same side hand--interesting concept to play with--
gotta think of some easier way to carry that high dollar firepower long distances without a gunbearer!!
-------------------- An armed man is a citizen of his country, an unarmed man just a subject.