My first car was probably made up of about 60% Bondo, and while that’s not what you should do with it, it’s still great stuff. I’ve used it for all types of applications other than bodywork. The trick in buying Bondo is to buy about five times what you think you’ll need. I found a gallon of their #265 lightweight filler over at Home & Beyond for just $17.46 — a pretty good deal.
Hey, sometimes it’s the only thing that’ll get the job done.