Okay.. I travel light.. I pack a few pants, enough undies for the trip, a few shirts.. and buy some extra shirts along the way. I usually camp, so I have a $30 buck 2-man tent from Target. The bulkiest thing I carry is a sleeping bag, which sits behind me and acts as a back rest. Sometimes I carry rain gear, but I hardly every use it unless it's going to be raining all day long.
My biggest worry is tires, but you have a Touring so your tire sizes should be readily available IF you have a problem. I never have had a tire problem on a trip, but I know 240/50-16 (or 240/55-16) tires don't grow on trees. You might take along some tire plugs and a can of fix a flat.
The main thing is enjoy the scenery. 5 days in Sturgis IS worth it. Ride around, see Mt Rushmore, Devil's Tower, etc.. Hit a concert at the Buffalo Chip.. it's a BLAST, even if you just sit back on your bike and enjoy the show..
I plan on going again next year.. My buddy's sons turn 21 next year so we're going to ride up there and try not to get caught getting in trouble.. lol