Roasted Could be me, but i dont think this is supposed to happen, is it?
Thank you for reporting the visual glitches.
Here's the updated mod package
Screenshot of cannons with decals:
Dead pixels along cannon roofs are mostly gone.

Issue:
Cannons roof sprites contain semi-transparent shadows which are similar to glass armors.
When roof decals were rendered in opaque colors, these shadows became black pixels.
Workaround:
Added one line in roof_colored.shader
to leave semi-transparent dark pixels untouched when rendering roofs.