The following is the next iteration of my RockSim model.
So far, I have cut the bottom tube and the transition section, and made a custom ring to adapt the 29mm mount to the upper 2" tube. I have a hole saw that was just a skosh too big for that tube. That works fine as I merely attached a bolt, and chuck it up and to sand it to fit. I have another saw that is about perfect for LOC 29mm tubing. After the JB Weld has set on the retainer, I'll complete the motor mount stack.
The hard part will be trimming the fins. I hate cutting ply with a razor blade. I started each end of the cuts on the first fin using a thin Dremel wheel. Despite patiently cutting out the first arc, some the outer ply on one base tip basically crumbled off. I plan to glue on some 1/64th balsa stock to fix it up. I suspect this will happen again.