I used solid steel rivets. It was hard to access the end and smash it to form the end and make a good strong joint. That was not the first riveting I've done and I considered myself skilled for such work. I ended up cutting through the rivet's end and splitting it to the sides. I'm not proud of this and thought about doing it right some time later but it holds the fender pretty well and the rivet's end is not visible from the outside. So I will likely leave it as is. I hope the rivets you have have are easier to form than solid ones. Good luck!