True, It would be a kit. The mold is the hard part but my friend does it all the time. He also analyzes the stresses and builds the laminate schedule. We would use carbon fiber, he is a dealer of this material, engines I’m considering are Rotax, Verner, D-Motor. All these are under 180# less prop. There is also a Higgs engine that may work. Probably just design for a MGL or GRT all in one flight instruments for simplicity and light weight.If you are going composite it’s a new design with the exact same shape as a WAR. 500 lb would be impressive. The firewall forward is going to be 250 lb engine, prop, cowl, and other stuff. 250 lb airframe will be impressive, especially with retractable gear. At least for the shape and surface. I’m sure you can loose some weight, substantial I’m sure. Half weight is pretty ambitious. Easier to build once the moulds are done, sure; but building the moulds is part of the job; I bet it’s not zero hours. 500 plus 1000 making moulds probably another 500 for systems. Canopy, flight control runs, fuel lines, landing gear, wiring is not going to be free time. If you are turning it into a kit, I bet plenty will be able to capitalize on your hard work laying everything out, but the first one will not be that quick.