My son need a top box for his Ffazer 400 for college and since there are no racks that I could find made specifically for the 400, I modified a part of the givi 340f mono arm kit to fit and made up a new bracket. I documented how I did it after a fellow from Greece asked about fitting a rack to the Fazer 400 and uploaded the file to: Downloads » Manuals » Fazer 400 » Fitting Givi rack to Fazer 400.pdf.
The only extras I added to assist the fitting was a used pair of rear indicators from the Fazer 600 as they are longer than the 400 ones helped when fitting the mono arms