The HD Duece sissybar mounts under the seat, not to the fender struts. Before I mounted the Duece backrest, I looked at a lot of sissybar setups and the one that looked the closest was a Honda Shadow. If it were me, I would head down to the Honda Dealer with a tape measure and check the distance between the fender strut bolts and the width of the fender. There are plenty of aftermarket places to get honda accessories from to possibly work for you.
BTW, when are you going to post a pic of the whole bike? The ones you have posted look good.
