i'm not sure either, but you may have to grind off the 'loop' the back seat slides under?  my 2005 model doesn't have that loop with the 1 piece seat.

What are you doing with the fender and the wiring attached thereto?

i'm sorry..i misunderstood.  i thought you were going from a 2 piece seat set up to a 1 piece seat off the newer models.  

yeah..hiding the 'stuff' is the tougher part.  though a lot of folks relocate the rectifier and then just put something over the mount holes i think.  i wish there were a 'rack' of sorts that would fit directly on there with a solo seat so that area would be useful.  

something like this:

They make leather covers for fenders to cover left over holes.  I made a mount out of wood and fitted a Celtic belt buckle to it to cover the holes left over from the stock tail light, I'm sure a luggage rack could be fabricated to utilize the holes left over from the passenger seat and tail light. Just map it out on a piece of cardboard and start bending metal tube stock!