I stopped by the body shop today, but didn't have my camera with me. That's OK, because I left the shop with a small momento.
Neal (one of the body shop guys) removed the rear bumper, and had difficulty reaching one of the bolts on the passenger side. This is the area with the known body damage. He started probing the area just under the gas cap with a screwdriver, and was able to pop off the following slab of Bondo from the rear 1/4 panel -
Once I got the slab back to work, I weighed it on a postal scale - it's over 2.5 lbs of body putty!