Here is the replacement panel from my donor car.  I basically cut it down from the corners of the trunk opening and along the bottom of the trunk floor.  This wasn't a perfect panel by far but the lines around the license plate area and the fuel filler were pretty straight.  Someone had cut a hole in it too for a light or something and I filled that in.  Then, I held it up on my car and marked an outline on the body for reference.  I then came inside of those lines and marked where the panel would join the car.  The bottom edge lines up along the bottom of the license recess area which made the blending in easier.  Then the measurements were adjusted for the overlapping flanges, measured again, measured again and again and then CUT!  Finally, the panel was trimmed a little at a time until it fit the opening great.

Now that the sheetmetal parts fit, the flanging and drilling commenced.  I used a flange tool from Harbor Freight that left a nice 1/2" flange along the edges.  That tool also punches holes but they were too large for the 1/8" rivets I was using.  Next, I drilled 1/8" holes around the patch, matched it up to the body, marked the holes and drilled the body.  All the holes were ground smooth.  Then, I used Eastwood's countersink tool to get the rivets flush with the panel.  In hindsight, I wouldn't recommend this tool as it created more problems than it solved by making the edges pretty bumpy along the edges.  I won't use this on the quarter panel..

You can see the results with these tools.  With the adhesive I am using, the rivets were only needed to pull the items together.  I ground them smooth after the adhesive set.  Holding pins or sheetmetal screws would have worked too.