Don,
That model A has the posts pie cut just above the top mounting bolt................perhaps it's just a terminology thing, when you say Z'd you meant pie cut. Pie cut is basically a V shaped piece removed and the remaining rejoined. Z'ing would have made the pillars return on itself at a different plane.

Here's a pic and a link showing a similar concept on a Deuce. In this case, new lower stanchions were cast to accomplish the layback. http://www.roadsters.com/rodwell/

Early Austin Healy afficionados will remember the 100-4's had a laydown windshield feature too..............for streamlining in race events.

I would suggest you don't want to totally eliminate the "brow" effect on the top from an esthetics standpoint. True, it corrupts the aerodynamics, but I think it would be difficult to get a "flush" header bow shape that wouldn't look truncated unless it had sufficient loft and flow.