We placed the plexiglas lense cover over the hole and marked about 3/4 inch overlap on all sides. To cut the plexiglas I dropped it into a bucket filled with hot water to heat-soak it and avoid cracking. Then we cut it to its new size with a band saw and hand-edged the edges with Scotchbrite pads.
I used strong duct tape to pull the lense forward and, making sure it was placed correctly with even overlap on all sides, drill each hole to #40 and cleco'd the hole. I ended up with a pretty good fit.
Then I made sure the mounting strips fit properly on the plexiglas, final-drilled the screw holes in the plexiglass and mount strips, then deburred and countersunk the plexiglass and mount strips for screws and rivets. Finally I primed the strips.
Sizing and marking the lense cover
Pulling the sized cover into place, drilling holes
