I hunt woodcock which is a similar bird using 1 oz. RSTs as well. I use an IC/MOD combination in my sxs with #8s in the right barrel to fill out the pattern and #7s in the left for when they get out away. I've tried Polywad spreaders which opened the pattern even further with good results.
I use different size shot in each barrel simply to make the most of having two barrels and chokes.
Hope this helps, Karl