There's no curvature in the top of the fender and that's what God invented hammers and blocks of wood for. If you want to be nice, grind or whittle the edges of a piece of soft wood like pine so that it's close to the configuration that you're after and supporting the upper outer end, use your block and clouter to make the curve you need. Slow, easy blows should do it, but if the top is really strong, you may have to "give 'er" a bit. Mind the windshield or better yet, take it off and do it on the bench with many checks for effectiveness. You'll have to bondo up some wee dings, but that's life. Good luck.