Hi Sarah,
I had the Metal Mule exhaust on my previous XT660R. I fitted a set of Fehlings crash bars to it and they worked quite well. The right hand bar needs the middle fixing tube sawn off, and I had to cut a slot in the (Touratech) bashplate for the lower tube.
http://www.ebay.co.uk/itm/Yamaha-XT-...item5d51b20881.

The instructions are in German, but installation is quite simple.

Scott.