I'm not sure if you can tell, but the corners of the long ends isn't square. It's rounded. Back in college I was shown how to use this strip heater to soften plexiglass so it could be shaped into a small picture holder. That stuck with me and I've been wondering for years if I could do the same thing with a heat gun. Turns out you can.
The trick is to control where the heat goes. You want only a narrow band heated. I accomplished this by putting aluminum foil over the plexiglass with only a millimeter or two exposed between sheets. I used masking tape to hold the foil in place, but put the tape on unheated side so it wouldn't melt or catch fire or something.
|only a mm or two exposed.|
I clamped the plexiglass to a bench, slowly waved a heat gun back and forth over the gap, and gently lifted on the unclamped side. After a few minutes I was able to lift the loose end further and further until it was at a right angle. The outside of the curve had the same arc as the edge of a quarter.
|At a right angle.|
If I were doing it again, I'd have a dowel rod handy to wrap the plexiglass around to make a nice curve.
The ends were cut out with a band saw. It was all sealed up with silicone aquarium sealer.