I built one many years ago, when the kit first came out. A brother built one as well, although he modified his by switching the fins, putting the larger booster fins on the upper stage, and vice versa. I was very skeptical of the 'pop-and-go' staging since with previous two-stagers I had witnessed more than one sustainer ignition failure for something as simple as not using a tape seal between the two engines, but both birds had many two-stage flights, every one completely successful. It was a great design and my first D-powered bird and, at the time, my all-time favorite Estes rocket.

Joe