Little update:

I've begun the drawings for the backplate/supercharger/valvetrain assembly. I also figured out another way to use poppet valves just in case...

It would end up being a 4 valve hemi - head with smaller exhaust valves and a centered glow plug. Very common in full-size engines, but I haven't seen it in small glow engines. Does anyone know if there's a smaller diameter glow plug? That would help with the valve size if I end up designing it that way....