So, done a little early with the exercise vetting.
A little something more current for Friday's workshop.
Just about anything that is (or will fit around) a tube can be launched. In this case I just reduced the Falcon 9 by 65% to get it down to something just a little bigger than the 1/2 inch PVC tube's (.84in/21mm) outer diameter. Obviously deleted the engines and eliminated all internal formers but the top one - serves as the pressure bulkhead. Also took the "corner" engine fairings and creased them to make fins.
Addendum-needs larger fins to fly well; might modify or just leave it as a display piece.
Mike, saw your post. Looks like a neat idea to both extend the duration of the impulse and potentially reduce the weight of the rocket (assuming you build the lower section lighter/un-reinforced) with the only strong structure concentrated around whatever the rod pushes on.
Yogi