[Bruce Edwards]

By that do you mean the car manufacture said it should have a gap or the windshield manufacture said it needed one?
The windshield gets it strengh from the curve in the glass not the frame. The uprights that hold it in place should not move and if the windshield is flexing in the middle I would be a bit concerned. The way the frame and glass work together make it fairly strong, after all you can attach a top that is always trying to tear it's self off the car by pulling up due to the wind force.
I guess my problem is I do not drive at 150 mph and have never seen one move once it is bolted into place.