I FINALLY figured out how to make the skyboxes display at their maximum brightness. It was as simple as editing the ASCII of the model and recompiling! I just had to set the self illumination and ambient stats to maximum, and it worked!!
Now I can re-render the shots (this time including Peragus) at their original brightness without any extra glow effect, as this will be added in-game. My only concern is editing the model, as it's possible that the M4-78EP does this as well to correct the UV mapping on the M4-78 skybox. Perhaps I can incorporate this into my mod, maybe even correct the UV mappings of the rest of the skyboxes.