The image of a windshield on a vehicle template invariably is wrong. The problem is that to get a proper image you have to flatten out a three dimensional object.
Simple to do. Tape a piece of paper across the windshield. I keep a roll of 24" lightweight white wrapping paper [available at any office supply store] on hand for just this purpose.
Mark the outline of the top and sides of the windshield with a sharpie. Just follow the edge of the glass. In your case you only need the top curve and a few inches down each side.
Remove the marked paper and tape it flat to a table or, better, to the floor. Draw a straight line across the image from windshield edge to windshield edge. Measure the length of this line and note it somewhere, right on the paper is good.
Take a picture of the template standing right over it. Try to keep the camera lens as parallel to the paper as you can. Import this picture into whatever software you're using and make it full size based on your measurement. The easiest way to do this is to draw a rectangle around the image exactly the same width as the line you drew, map the image into the rectangle, make the rectangle as wide as your measurement keeping it proportional, and unmap the image. Now you have a reasonably exact image of a flattened windshield.
Fit your text to this image. Depending on the curvature of the glass what you end up with might look counter-intuitive to you. Never fear, it's correct and it will fit the top of the windshield like a glove.