I myself have recently modified the "official" Indiana Jones fedora to make it appear closer to the Raiders model. I accomplished this by doing two things, I re-creased the crown so that it actually sticks up higher and I pinched it with a clamp for a couple days, periodically dampening it to allow the new crease. I also re-creased the edges of the crown and it led to this...
Still not COMPLETELY done yet, I still need to finish the creases, because they eventually drift back towards the pre-made shape. Any ideas as to how to make it hold the shape better? I also need to make the material itself look weathered.