The common step over seems to be around 9% ( Tony you posted before I could add mine but we are in agreement....
As for the Lexan, one note of caution.
The reason Lexan is used to replace glass is because it’s “ flexible “
I did a fair amount of installing Lexan on church windows to protect them from breakage.
It works well ,,but it’s also “soft”.
Cast acrylic would be a far better choice to produce a quality.
But I also know, what you get is what you have to work with.
I have run the same file in the reverse direction to clean up the leftovers.
Best of luck on the venture.
Post pictures of your progress.