I may be wrong (in which case I am sure someone with more info will correct me), but I believe that sporrans were traditionally worn to the side. Now I am not talking about the formal outfits, but rather the Highland Scots that wore their kilts on a day to day basis. I hate refering to a film for a reference, but in Rob Roy you can see that they all wear their sporrans to the side. Check out a Freelander sporran http://home.c2i.net/kilted_1/public_html/ , as it may be perfect for this and for dressier use.

As for using 2 sporrans, I have only done this once or twice. I have used a day sporran around my waist, and have used my clan tartan sporran from Bear Kilts http://www.bearkilts.com/sporranpg2.html over my shoulder and under arm (under a jacket of course) as the sporran and strap are soft enought the fit withou being bulky and cumbersome. A passport case or neck money belt can also be used this way.