I'm doing my own custom csp's for cbliss, i extracted the original ones and their size was 102kb, and the ones i was gonna replace them with were 58kb, but when i replaced them i noticed the common5.pac was even bigger than before replacing the csps! so i extracted my csps and now their size was 144kb.
The original images were in CMPR format, so i gave that same format to the ones i replaced.
Is the MIP level more than 1? That could be the possible reason you have a bigger image file.
yes, the MIP level is set to 1, CMPR with MIP level 1 is the lowest file size i've found for csp images. I also tried using the posterize option in photoshop to reduce the quality and size of the image and indexed colors but it didn't work