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.

http://carnival.saysuncle.com/001086.html

and

http://precisionlongrangehunter.com/articles_shooting.htm

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!!