You can make much better smoke with ping pong balls or a 3:2 ratio of KNO3 and sugar in an old motor casing. ;)

Although the designs of the Concept II are really nice, The exchangeable mount could become a problem. The three different motor mounts use a single plastic centering ring with two slots that let small tabs pass through, then twist to lock. After a few flights the plastic ring would start to deform, making removal and installation difficult. In retrospect I think if wadding was packed around the mount before installing it might have prevented the problems.