High Altitude Rocket Project (HARP)

While we establish goals, perhaps the goals themselves may be constrained by what this thing should be made of. Obviously the overall weight goal is 'as light as possible', but knowing what the general loads are on systems such as HARP, what are reasonable materials to consider? For example, should we have a goal to use traditional materials (paper, balsa, plastic) or are these unlikely to survive the air friction and acceleration that HARP will experience? Has any work been done in launching a fairly large rocket made of paper tube, balsa and plastic to Mach 3? Requirements are constraints, so are materials a constraint? If they are not, then materials may be constrained by what the engine type will be. For example, if I were to use clustered F series engines, which I can buy off the shelf, can I reasonably get something flying towards the goal, relying on paper body tubes and ply or birch wings? So an additional constraint is this: use prepackaged engines, or do we pack our own? Is it even possible to use prepackaged engines for an endeavor such as this? I saw a post of someone who got a rocket to a pretty good altitude on 5 daisy chained COTS engines, by packing them all in series in a tube that protruded out the back of the rocket. Each engine's ejection charge simple ejected itself overboard along with an expendable coupler. The weight and balance dynamics would be interesting but not much different from a classic multi-stage rocket. Anyway, food for thought.