That's what there may not be room for. Ducati makes an expensive tool shaped like a C that curves around the edge of the head to grab the head nut. The inexpensive tool is an extension that you attach to your torque wrench but needs a little room to work. It can also be made from a wrench with a socket welded to it.
Here:
http://www.bevelheaven.com/stuff-for-sale-headnut-wrench.htm And here:
http://motoreva.com/item.cfm?itemid=103&categoryid=171Scott
