Having been involved in the speciality car business most of my working life, I found it far easier to take a shape and modify it than start absolutely from scratch.
You just need something that has a similar shape to that you want - in my day that would be Cobra, Porsche and Jag bodies ! That approach works well for bike panels as much as anything else.
Lots of possibilities - Downhill toboggans, sidecar tubs, land yatchs, one man kayaky things.
All of the foregoing has added fuel as to the validity of the original quote from the unamed author.........................
I rest my case.