[DougD]

krausewich
Are you planning a top, and more importantly, side curtains? If so, I'd strongly suggest you obtain at least the sidecurtains before permanently securing your windshield. Set the windshield to the angle that will fit the side curtains snugly.
If you aren't planning a top or sidecurtains, then the windshield angle is not that critical. The angle can be measured by placing an adjustable square with a leveling bubble in it along an imaginary vertical line at the center of the windshield. I believe most use 45 degrees.