When I got my bike, the tank had a golf-ball sized dent in it from the previous owner. Apparently it fell over in his driveway and the bars transferred the blow into the side of the tank.
I recently stripped it down and went to pick up some bondo only to find that the smallest amount I could get was a quart for $14
Now, If you are cheap like me, spending $14 for way more of something than you need doesn't make much sense. Instead, I picked up some JB SteelStik for $4.
It worked well and I'm sure its stronger than bondo, too. It took a little longer to sand, but in my opinion it was well worth it. Also, I have a lot of it left over that I'm sure I will use in some fabrication I've got in mind. Just thought I would share.