tamathorn, I made a drivers backrest out of a inch and a quarter wide by 3/8 thick flat stock from homedepot. Notched one end that will go (slide)on the bolt that holds the front bracket for the passenger seat. I first made a template out of a piece of cardboard to get the curve I wanted around the passenger seat. Then heated the flat stock to match the template. By the way, I took the center bolt that holds the passenger seat on (and will hold the new bracket) then replaced it with a longer bolt from the tire side with a lock washer, the head of the bolt cleared the tire easily. It will give you a little more threads to run the nut and washers up to allow the bracket more room to slide in. I also notched the passenger seat bracket to allow a wrench more room to turn the nut to tighten the down the backrest bracket. I used a oem wide backrest pad from yamaha with studs to match the silverado passenger backrest. I had to leave the flat stock long and put the drivers seat back on to get the heighth I wanted for the backrest pad, then cut off the excess. Then welded a tab on both sides of the inch and quarter flat stock and drilled holes where the other two bolts will go into the pad. I had to work with the angle of the flat stock a little to get the comfort I wanted. I laid the bracket on a flat surface and traced on the surface the curve of the bracket so I would have a starting point to adjust the curve. CAUTION: DO NOT TRY TO BEND THE BRACKET WHILE BOLTED IN PLACE. IT WILL BEND THE FENDER BEFORE BENDING THE BRACKET
THE VOICE OF EXPERIENCE.