Though I went another direction, I thought long and hard about the OXFORD Sport panniers. They expand out, away from the rear fender, and look like they could hold quite a bit. I did not think they would look too out of place on a Black Speedmaster, either - not having a luggage rack or sissy bar at the time.
In the end, I went with the EasyBrackets and Willie and Max Standard Touring saddlebags - for less than $300 for the whole set-up, and they are as large of a "leather-looking" saddlebag as you are likely to want, to look right, anyway.
The only reason I did not go with the Sports panniers is I did not want to have to drill them to use EasyBrackets.
Now if I had a Sprint ST1300.........
