[Christ]

Radius doesn't equate to angle, though. If the angle between windshield and roof is only 45 degrees, the air being forced up the windshield at high speed may detach at the roof line, if the transition radios is less than 4". The bubble idea would create an optimal radius from the angle, training the flow back onto the roof line. With proper tapering, the bubble can also lead into the rear departure, lessening the required length for a boat trail or kamm shape to be effective, by increasing the angle at which they can be mounted relative to horizon.