I used to build rockets when I was a kid. My 10 yr old son found a 48" x 5" plan tube in my office and asked if we could construct a rocket from it. We used a traffic cone from a model race car set, an 8oz clear drinking cup for a crew module (for 2 Lego astronauts) and cut the fins from a sheet of Lexan. We constructed a jig to build it all exactly square, with particular attention to the fins and nose cone alignment. Then we built an extra large launch pad. I ordered (2) 3 packs of E12-6's, figuring we'd do several shots. Tito decided we should load (3) into the first launch. Alrighty then! We taped 3 engines together, then wrapped them in multiple drink kuzies until they packed tight into the base of the rocket, then wrapped those in friction take to hold the engine pack in place. Made a chute from a Hefty garbage bag. We bought a pack of high energy ignitors so all 3 engines would light simultaneously before the rocket began climbing. We used my truck battery as the power source to get the fastest ignition possible. It was IMPRESSIVE! These E12's are everything they're advertised to be.
Here's a link to the flight: https://www.youtube.com/watch?v=olAdn33yvJ4