Scratch built body and motor question

The Estes Mean Machine was six feet long, four 18" airframe tubes. It used a single D motor. So the answer is "at least six feet long". Possibly longer if one used a cluster of motors or added a bit more BP to a reloadable motor ejection well....

Terry

You could have a body tube of many, many feet in length. You don't need to push the nosecone out the front end for the recovery system to work. You can break it in the middle, or just in front of the fins if you want. You just need a securely fitting plug or transition joint at the place you want it to come apart.