This is a 2X upscale of the Estes Ram Jet kit, which I built about 25 years ago.  BT80 outer tube with a BT55 core tube (which is the original's outer).  24mm mount for 3.75" motor case, 18 custom fit vane fins and 3 large 1/8" balsa main fins.  I papered the main fins, since the wood seemed a little soft for my taste.  This project in ongoing, so I haven't yet added any recovery equipment or launch lugs.  Once I have everything filleted and primed, I'll weigh it to get an idea of chute size.  I purchased Excelsior decals for the BT80 upscale, that was the inspiration to build this.