Roof plug 12.

Not so much the roof plug, but still relevant to the overall work in progress.
Davesideways highlighted an important idea, a diffuser, and suggested the Lotus design be looked at and maybe copied.
Also, suggested installing front radiator , sticking ribbon, at rear to view air flow, before installing radiator.
When the prototype for first roof was fabricated, we tied string, to boot area, and observed flow into boot. But this new design hasn't had that benefit.
So prehaps a section could be removed from boot floor, a diffuser incorporated, and extra guaranteed flow directed towards rear radiator.