The way I am going to be doing it next time is use a caliper to measure the screen dimensions while it is lit up then transfer to the box with a sharpie and use a small drill bit to go around and perferate it of sorts then cut with a cut off disc and snap off the excess then clean up the rest with a dremel and hand files. If you look at my build the window for mine is pretty ugly and I think this approach would make a very neat and tidy window.
Yep, preparing the enclosure takes time and patience.....haven't found an easy way YET.....