@Joe69420
Message me if you have issues, and don't 4bpp grayscale any images that have actual gradients.
8bpp is a safe way to go for any non-color pages.
4bpp works on any pages that are high enough quality raws, and only use patterns and no gradients. Test and compare.
For color, you can test the 8bpp pingo color option. If it's got really bad banding, try the same option, but manually uncheck the "-nodithering" option. If both are too crunchitized, just do the "No Preset" option and run it on the color image in order to get a small, lossless optimization.
For example, I 8bpp'd your credits page.