This is what I have done:
Windscreen = 3/4" all around
Door windows = one-inch all around, put a large radius at front lower corner.
Rear lexan = 1.5" at the top to match the "horseshoe", and 1" all around (except at top). I have cut mine this way, but have seen a 2" all around that looks good too with black borders.
Note: if you plan on using high door mounted race mirrors, you will need to leave a
good bit of a triangle shape in the upper front of the doors to attach them (exact shape to be determined by the mirrors used). The lexan side windows will also need to be trimmed to suit. There should be no issues with the upper door hinges.
Others may differ.