Besides having a cheap track car, I also bought the CRX to try out different things, so this past weekend I made up Lexan panels to replace the rear side windows.  Once I had the window removed, I traced the outline onto a piece of cheap Plexiglas from Lowe's.  The shape was cut out using a jigsaw with a 18 tooth/inch blade.  Once the Plexiglas was cut, I made fine adjustments with sandpaper until I was happy with the fitment.  Now that the template was completed, I bought a sheet of Lexan, at Lowe's and basically complete the same steps - traced the template, cut out with jigsaw and make final tweaks with sandpaper.

Before I secured the Lexan panels, I had some other work.  There were four holes that were used for clips that were welded closed and I sanded, primered, and painted the area where the panels are secured.  When the paint dried, I lined up the panels, drilled holes and secured them with screws and nuts. 
 
I still need to mask off a border area on the outside of the panels and this area will be painted black.  This will clean up the look of the panels and create a finished look. 

So far, I am happy with the way the panels turned out and learned some stuff for next time, which will be the rear hatch glass.  As a side benefit, the new panels weigh five pounds less than the side glass panels.