Bit of a thread resurrection here.
I eventually purchased a 1999 Ford Transit RWD cab chassis that I will use for the basis of the project.
It has a more angular front than the Kia I was looking at, which doesn't line up quite as well with the template, but the Kia was pretty blunt in plan view.
FWIW, it has had a Buick 3.8 V6 conversion and is quite light when naked but has a 2.5 tonne payload with an open chassis that will allow easy mounting of batteries above the prop shaft.
I've overlaid the aero template but am unsure how flat the roof would have to be before I start the teardrop?
If I can move the template further forward, then I can probably extend the template to the 22degree line and still fall within the overhang limits.