Ridiculousness of minimum diameter rockets can of course be measured in units of Curt Von Delius. For example, fins on a minimum diameter rocket that have a span 1.5 calibers are about 45% kurt von delius. Scratchbuilding ups the CVD coefficient, giving you about 75% Curt Von Delius for the aforementioned scenario.
In my case, I accidentally went full CVD. (Well, almost. I have an airframe. That gives me about 95% CVD).
100% Scratchbuilt carbon fiber MD with the motor case acting as the coupler. The fins are 9 layers quasi-isotropic 5.7oz plain weave carbon, at about 0.085″ thickness.The airframe is 4 wraps of 5.7oz plain weave carbon, about 0.045″ thickness.
The motor is a Loki Research 54/2800 case, with either Soylent Green or my new ‘Supernova’ propellant. Expecting Mach ~2.5-3.1