I use the Polywad, 2 1/2-inch, 7/8 oz. DoubleWides in my 1893 Quality A-1 with Full/Full Damascus barrels. The DoubleWides (spreaders) work nice with the tight chokes for most shooting. RST also has a nice lineup of low pressure 2 1/2 shells.
I would also have a good double gun smith look at the barrel wall thickness of your Damascus barrels. Please see the FAQs section of the website for the recommended barrel wall thickness measurements.