Just because you think you can make a panel don't go bad mouthing others. We have sold many of the rear fender panel and I have installed many. They fit very well and are very reasonable price wise for hand made parts.
I wouldn't get to deep into it any way soon they will have them from China dirt cheep
Heres how the big boys do it
http://oldgmctrucks.infopop.cc/eve/forums/a/tpc/f/237106068/m/1771015251