I found this conversion for the passenger backrest on another forum, it is easy and looks pretty good. I bought everything but the turn buckles (lowes) at ACE Hardware they have a great assortment of chrome bolts, acorns and washers.
2 1/4" X 1" coarse thread hardend bolts. Replaces the 3/4" long bolts in the front saddle bag supports reuse existing washers.
2 Turn buckles stainless steel. you want them to be 5" center to center of the eyelets with the eyelets screwed almost all the way in.
2 Nuts to fit on the right hand threaded side of each turn buckle to act as a locking nut
2 Chrome 3/8" X 2" allen button head bolts. varify this length, it must go through the eyelet, spool, washer and engage the cap nut.
2 Chrome washers for 3/8" bolts
2 Chrome 3/8" cap nuts
2 Detachable hardware spools from HD. I used leftover spools from an old two point docking hardware.
2 Rubber bushings 1/4" ID 3/8" OD approx 1/4" long. These will be used in the lower eyelet to take up slop between the 1/4" bolt and the eylet.
I am going to paint the turn buckles gloss black to make them look better but the seat is rock solid and looks great