I also don't want to give building-hints here. you will find help at the R2-Builders-Club. Building this Astromech was pretty much the same as my R2-D2, except hte head. With the experience of my first R2-D2, I made some improvements to it. By the way. This droid really apeared in the movie. When the Emperor arrives on the second deathstar, you can see it for the fraction of a second in the background.