How about a paper and foam Project Orion Battleship (the bigger one in the attached photo)? A diameter of 12" results in an overall length of around 35". Since I have no self-imposed requirement to fly on 29mm motors, I guess I'd go for a 38mm mount. This will take a lot more planning, including a source of the tubes to form the 12 'shock absorbers'. It would probably have a 4" inner tube just like the Too Rolling (Red)Stoned. This would also let me re-use the cone from the Grand Whazoo (about the only surviving part). As for fins, I think I'll try slide-in units that fit in 4 of the piston tubes.
Brain swimming...I wonder if a big wire spool would have a use in this thing? Could I make the pistons functional? What then to do about the motor tube?
Yes, this will take some head scratching and scrounging.
I rate the chances of me actually building this as...well...just enough to warrant its own tag.