Bill, funny that you mentioned putting a drain there. My painter and I, talked about doing this for a while, but instead we settled on using POR 15 in these areas, for future rust control. As you know, the water gets in, and can't get out. I had a descent idea of using a stainless 5/16" tube with a flare on it, similar to brake line, and shooting it down and through the trunk pan, but I chickened out, and bought some POR 15.
These areas on my car were gone. The previous owner used steel wool, or it could have been an S.O.S pad, and covered it over with good ole Bondo.
Let us know what you end up doing.