On my '06, there are 3 bolts securing each luggage antler to the frame.  Two by the grab rail and one close to where the luggage latch is located on the side by the passenger foot rest.  From all the pictures I've seen, it looks like that 3rd bolt is not supposed to be there (no hole drilled) but instead just a rubber bumper between the frame and the antler.  My right antler was broken when I bought the bike so I suspect the PO secured it by drilling through the antler and bumper plate welded to the frame.  Both antlers have been drill and bolted.  Problem is, with the bolt tightened, the bag droops and hits the rear brake caliper so if it's not necessary, I'll remove the bolts (rt. antlers has been repaired) and shim the bumper accordingly to prevent the bag from hitting the caliper.

Here's what's going on. Yes, the po added the 3rd bolt. I did it to mine, with a shoulder so it can't be overtightened, and it holds the antler in connection with the bumper. That's not the reason your bags droop though, the actual bag mount is an encapsulated rubber mount, like an automotive engine mount. What's happened os that the rubber has broken away from the mount internally, and the bag then sags. Check it out, you'll see what I mean. Steve

Steve, you nailed it again!  The right side is much looser than the left.  Once the rubber mount breaks will these eventually come apart or can I install a collar on the bolts that the PO installed and go merrily on my way?  It's already hung on for at least 10K miles.   Yikes!!!  A new one is $75!

Steve's exactly right.  I've added (glued) about a 3/16" dense rubber shim the size of a quarter to the pad on the antler where it contacts the frame to push it back out to compensate for the twist.
My dad had used a 1/4" threaded rod thru the fender to make an adjustable brace between the two cases.  Two small holes were in the fender with each end having a pad that rested on the bag.  It kind of just floated there in the fender keeping straight.  Each bag would effectively push the other outwards with its weight.  It was adjustable but kind of overkill I thought.  He did however carry a LOT of stuff in his bags all the time.  He was always ready to go somewhere.  If you've bobbed the fender this won't quit work the same.

I have a pair of 1 1/2" furniture pads stuck between each of my antlers and antler pads (near the side latch).  This helps the bags stand a little more proud, and cushions them slightly on bumpy roads.

I bought them at Lowes.

http://www.lowes.com/ProductDisplay?partNumber=54257-255-4738495N&langId=-1&storeId=10151&productId=3034740&catalogId=10051&cmRelshp=rel&rel=nofollow&cId=PDIO1

Thanks for the help.  I've got 2 extra bumpers from when the PO put new bags on the bike before selling it.  It looks like their going to work fine.