I had the first on the JP Cycle page and cut the plastic that the bags are attached to between the small andlargebags and loosened the screws holding my King Pin windhield together, slid the the plastic under the chrome strap and tightened them down. I don't have one behind the speedo but I have the other 2.
Not sure if any of this will work for you. It's not bike specific but may be worth a look.
Search the gallery for Winshield Bags under my screen name. There are 3 pictures, you will get the idea.