you might wanna try getting at them from the inside if you can and use bondo as sparingly as possible. it has the ability to crap and even pop out. as for the rust... the rusted part of the quaters needs to be cut out neatly enought of a new piece of sheet metal( cold rolled steel 12-14 ga. tends to be the easiest to work with since it can bend somewht easy from wht i can see) the new panels need to be cut out and shaped into the quaters meticulously. the new panels need to match the lines in the body, again you might think.... bondo... no thats the last step, you need to weld it in and hammer it pull it out, weld and then mold it to your bodylines. its a tedious process that wont come out good unless you are a good metalworker. bondo is then used to even out the surfaces of the new panels to match the body. again try to use as little bondo as possible. hope that helps!