Ya, it's for plugging the screw holes and a couple of minor molds on the edges of the pieces that don't fit together. I don't need as much of the bondo as the tubs come in, so this stuff is a little better for the size of my project. I also don't need to worry much about cracking because I'll be putting two coats of paint as well as the nickle colored weathering and the finish coats.
Oh, also, how hard would it be to get a shell in the shape of an E-11 which can hold a pistol-style RC car control? I had a cool idea about a MSE-6 droid...