Hi guys,
here's a link to the german xt660 site. they have a very intersting list of tail tidy conversions:
http://www.xt-660.de/mainframe.htm
Click on "Umbau und Zubehor" on the left side and then scroll down to "Heckumbauten" and click on the links. It's a german forum but has a lot of pics which do the talking!