[morgal48]

On the red renderings it appears that the leading edge of the hoop is higher that the trailing edge of the windscreen. This is what the C6 Corvettes had with their Targa top design, and it caused severe buffeting. Somebody developed an aftermarket spacer that fit between the rear hatch lid latch and the body to allow air flow and reduce interior turbulence. With the top off the cockpit was like one of those tubes people stand in and try to grab loose paper money. The 911 Targa did not suffer from that problem.