I'm a new 1200GS owner ('06) and I'm trying to decide how to configure my luggage.
I have two general ride types I'm interested in...day trips (100-300 miles) in the southern Appalachians (twisties, gravel roads, fire roads) and "limited duration (3-14 days), some camping, some hoteling" tours.
I currently have BMW Vario panniers and trunk, but want a top loading set of panniers with a more durable mounting system. So, I plan to sell the Varios and start over. I've decided to spring for some aluminum panniers (Zega Pro's, BMW or Jesse Luggage) and now need to figure out how to make best use of the space between the panniers. Having just watched Helge Pedersen's Adventure Touring DVD, I have an immediate bias for his system (aluminum panniers, huge camera bag with rain cover between them, tent and bag strapped to pannier lids).
So, I'm looking for "a bag". A duffel bag would work, as would a camera bag. I'd like to be able to open the bag from the top...so that lets out roll top dry bags. Above all...it's got to be waterproof. Period.
What I think makes sense is to attach a bag (preference is to position the bag parallel to direction of travel) in the space where the pillion seat and the hard luggage trunk box currently is. The advantage of this is that the panniers are able to be opened without detaching the center bag. Off comes the pillion seat and off comes the BMW Vario trunk bag/box and mounting rack. Once this is removed then I'd use the basic platform that is directly behind the seat to attach a bag to.
I figure the bag should extend out to the tail light...maybe slightly hang over....so about 20" long. Width would be limited to 13-14". Height could be 8-10"...but since I'd have to swing my heel over it to mount the bike...no more than that.