"Boy, you gotta carry that weight"
To paraphrase the Old Farmer, 'you can lift in one hand and downforce in the other and see which one fills up first.'
My solution for the Beetle (similar to Porsche) was to graft on a Tropfenwagen tail.
Center of pressure moves back. I should redo this with the new software I'm learning. The parts could be Booleaned together, it will probably bork the materials assignments.
edit:
This one has more aggressive taper because the engine cooling air is introduced into a vertical trough, Coanda nozzle.
