Well I’m stumped… clearly my (lack of) knowledge of the properties of the texture files is at fault.
The TBM is easy…and makes some level of sense. Theres an alpha channel which controls the transparency. If you overlay the image with a shade of black/white it will affect the transperancy in the sim. As seen below, the right side is slightly darker (as it should be since its a slightly lighter grey in the texture file, and the squiggly line shows up as completely opeaque in the sim, as it should since it is pure white in the texture file.
Thats where it stops being easy. Most other planes seem to rely on the default glass textures located in /official/onestore/fs-base/texture/glass. I found that I was able to create a basic mod which loads those default textures into the aircraft and edit them but regardless of what I do to the file, overlay colors, alpha channel, etc… the effects are extremely muted as compared to the TBM windshield… for example:
Either I am not understanding the proper way to edit these files (which is probably true), or there is yet another texture file that I havent found which it is using…